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Last Shelter Clash of Zones: Best Research Day Tips

Tech Your Way to Power

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Last Shelter Clash of Zones Research Day is a tough event to max out – you can only research one at a time and is a big resource, cash, and speedup day. But what separates YOU from the rest of the power is the tech power behind that bolsters your hero, troops, fight, and defence throughout the entire game. Unseen deadly power. Research is one of the most important elements you can win over your opponents, including APC parts, so let’s break it down and show you my best tips to help maximise your research COZ before and as it happens.

First things first – if you have been neglecting your research upgrades, buckle up and get grinding as soon as possible! Tech power makes a big difference in many ways, with arguably one of the biggest game-changing tech that transforms your game. From your troop power, hospital efficiency, clash of zones points performance and unlocking the full potential of your APCs when it all goes down in Kill Enemy, Doomsday and Eden.

Clash of Zones: Gathering Day
Clash of Zones: Research Tech Day
Clash of Zones: Hero Development
Baneblade Super Energy Core Guide
Doomsday Shop & Coin Spend Guide
Eden: Dissidia Beginner’s Guide
SX Legendary Ticket: Which Hero Group?
Seasonal Hero Recruitment Schedule
SX Hero Recruitment Timeline
Positions for Every Season Hero
Legendary Heroes Guide
Season 1 Heroes Guide
Season 2 Heroes Guide
Season 3 Heroes Guide
Season 4 Heroes Guide
Wisdom Medal Hero Trick Guide
Best Ways to Level Up Heroes Fast
How to Save Electricity with Buildings
Doomsday Season 1 for Beginners
Base Level 25: REAL Journey Begins
Is VIP Shop Worth Unlocking?
Is Project Hero Worth it?
How to Earn Hero Super Tickets Fast

Upgrade Research Building Level

It’s easily to neglect your research building where all these tech upgrades are available to you, in favour of buildings that get you to a higher base level, war rooms, troop camps, barracks and so forth. But it’ll eventually catch up to you if you don’t get this building upgraded for two reasons. The biggest reason why you should ALWAYS aim to have the research institute the same or within one level of your base level is because it improves your research speed. At building level 20, the building improves research by 100%, saving you on speedups, diamonds and generally the length of time to organically upgrade your tech research.

This makes a huge difference as you go further down the skill trees and unlock advanced tech categories at higher base levels. The second reason is that if you find yourself reaching the upgrade to unlock T9 troops for any of the fighters, vehicles, or shooters (HUNK, Meat Harvester,), it requires the building to be level 24 before you can. If your building is left at level 20 or worse, even lower. That’s plenty of building upgrades you need to save up for and frustrating nonetheless. Make it easy for yourself and upgrade as you go, so when you get there, you’re closer than you first realise.

How the COZ Points System Works

It’s the difference between upgrades, not the power level itself.

It’s not obvious to start off with, but if you dig a little into the details you can work out roughly (or accurately), how many base COZ points you’ll receive per tech upgrade. You’ll see the same research power upgrade awarded for COZ and hourly challenges which is +400 base points. So that means per 1000 research power you get 400, which is 40%. Easy enough.

Now, like building power (which is covered in COZ Building Day guide), the actual points you receive is NOT the value for the tech level you’re upgrading to, but

Upgrade in Advance, But Not TOO Early

This is a basic you may already know, but you should be planning your researches in advance! You don’t need to wait for the actually day to arrive to start them. Like with gathering day and building day, to avoid wastefully using diamonds or speedups, get them started so once research COZ starts, the remaining time is far less that they land without needing to use ANY of your speedups.

Unlike gathering or building day, you can only have one running at a time, so you should plan the most time intensive and hiighest COZ point upgrade first. Lock those resources down now as you may not have enough for later if you don’t do them first.

You should always leave AT LEAST 2 hours after reset to ensure they land and you score points – sadly, it’s painful when you hear teammates missing out on valuable points as they fall just short of when COZ opens, which is 30 minutes after reset.

Even better, if you have access to an hourly challenge, plan your research so it organically finishes in the hour you want to land them on – just be sure to use that 100% COZ ticket and like before, leave a buffer so you can double dip on two hourly challenges to maximise COZ points.

Limit Your Overshoot for Another Hourly

It’s hard if you’re in a state or alliance at an early stage when COZ tickets are hard to come by. Be patient and work with what you have and try not to be persuaded by the game to spend real money on small bundles that include a 50% or 100% ticket. Trust me, they aren’t worth it as you’ll freely earn these and have many spare in your inventory.

Keep an eye out for my best and worst packages of Last Shelter, but essentially, try not to greatly overshoot your score on the hourly challenges needed to hit the third chest. It’s easy to think we should cram in as many upgrades in the 30 minute window once you pop a blue or green COZ ticket, but if you’re at a stage when these aren’t a rarity, hold some of those speedups and upgrades back for another pair of hourly challenges to activate them.

If you don’t, you’re greatly spending diamonds, resources, and speedups when you could let time work on your side if you do another round of upgrades later in the day or morning. You’ll essentially get more rewards back to offset the spend with hourly rewards that can even give you enough to continue upgrading. There are 24 hours in a day and the same applies to COZ – be strategic and tactical with your tech upgrades, as with any COZ event.

Be Careful with Spending Courage Medals!

If there was something I would have wanted to understand much earlier in my journey, it’s courage medals. These are arguably the hardest in-game currency to earn organically, predominantly linked to the level of COZ chest rewards you unlock.

There are other ways you can earn courage medals to a lesser extent, which I covered in ‘How to Max Level Up Your Heroes Fastest’ guide (opens a new window). I highly recommend reading that to see all the ways you can earn them, but you’ll get most of them in daily COZ events.

Courage medals should ONLY be spent on Zone Commemoration first, which is a HUGE research tech you want to progress as fast and early as possible. Everything becomes far easier for you (not saying it is easy, it’s the opposite actually).

Earlier on, you may want to ‘max’ the top row categories, however, there is a tech tree called’ Basic Combat’ which you should not be doing. The first few which allow you to earn courage medals hitting zombies and early troop promotion are fine, but DO NOT upgrade anything else. They all require courage medals!

You may think 20 / 40 / 50 is a small number and see maybe 1000 in your inventory earlier on. But courage medals go QUICK and are in short supply to earn in-game until you max zone commemoration. You have to keep at it. For example, the latter stages of finishing up zone commemoration (which has taken me 5/6 months to reach), the last 3 upgrades alone need 10,000 medals. Per zone commemoration tree maxed, you will need over 10,000 courage medals. So yes, save them. I probably could have maxed zone commemoration in 3 months if I knew earlier.

Max Zone Commemoration

Following up about saving courage medals as early as possible, where should you spend these instead? Once you upgrade the research institute building to level 8, you’ll unlock zone commemoration and zone conflict tech trees.

In addition to Basic Combat which is available to upgrade from the beginning, you should not be spending ANY courage medals in zone conflict at all. Yet. Focus everything on zone commemoration for the same reason: it will be a game-changer. Zone conflict also requires courage medals for EVERY upgrade and if you want some context, it’s specific to Kill Enemy COZ events every Saturday which applies battle buffs and improves medical facilities but only for that one day. You’ll also need to max zone conflict for T9 troops, but that’s much further in the game.

For now, you want to focus all courage medals and aim to max zone commomeration long-term. In the beginning, save these upgrades to do on the day as they can be good COZ point earners, but once you unlock super rewards which open COZ chests 7 – 9, you should be upgrading each as soon as possible – they increase the points you earn for those COZ events. Don’t wait for research day so you can reap the benefits sooner.

X2 COZ Rewards are HUGE

Seeing that X2 is what makes zone commemoration worth maxing as early as possible.

Why should you max zone commemoration? it’s because the final upgrade literally DOUBLES the number of rewards you receive from COZ events. It’s called X2 rewards. For every chest that gives you diamonds, courage medals, wisdom medals, resources, cash, and COZ tickets, you’ll literally see an X2 multiplier next to the chests which give you each reward twice.

So instead of those 9 total chests, you can unlock for clash of zones rewards? You get 18. 18! The earlier you can get this unlocked, everything else becomes slightly easier, especially when you get into the Elite tech and upgrades towards unlocking T9 troops.

Base upgrades and building upgrades get easier with all the extra goodies you get, while diamonds are no longer a scarcity, but another currency you can use to help you in many ways. Keep an eye out for my article on the best and worst ways to use your diamonds in Last Shelter.

Higher Tech Value Upgrades

High on your priority is Zone commemoration if you have courage medals are always good ones to do on tech day, but as I mentioned the mid to higher level upgrades are the ones worth doing. Parts production is killer upgrades to do during research tech, provided you have energy cores but should be used as points filler and boosts rather than your core upgrades for a tech day.

You should aim to max out your APC tech starting with Class APC, APC I, APC II, and lastly APC III in that order, with class APC’s particularly useful for raider and farmer classes as they have special buffs. Maxing out means unlocking the 3rd hero slot as they greatly benefit you in many ways during doomsday battle, COZ Hero Day, and are the backbone of your fighting force.

APCs do need quite a lot of resources, so if you find the requirements getting a little too steep, there’s no harm doing the later APCs to keep your tech going, though expect longer research times as a result.

Lowest Tech Value Upgrades

If you can help it, try to avoid doing medical advancements on research day as they all-round award quite low COZ points, even at the highest level upgrades relative to other tech researches. The basic military is roughly similar but fares slightly better. As for usefulness, medical does have it’s advantages with hospital and wounded upgrades so I would suggest that. Military more for training speed, count and kill rate. Both take quite a long time and offer little base points in return.

All troop early skill trees are generally low value relative to the time they need but gett better as you progress downwards and at higher levels. Up to around the 50% mark or enhanced troops tech you’ll need courage medals so best to stop there if you want to advance the might, resistance, and counter buffs of your troops.

Parts Production: Best COZ Points Value

Parts tech is the best value research you can do during tech day to garner high COZ points, require the least amount of time or speedups to finish, and is less resource-intensive than other tech researches. You can mix between your core upgrades that help develop your base, APCs, and such with parts research tech as if you find yourself low on one or two kinds of resources, there are parts tech upgrades that only require one or two kinds which you may have a surplus of.

These are best done when you need to close a big gap to your next chest, finesse the COZ points to finish as close to the target without massively overshooting on expensive research tech upgrades better used for another time or to simply find best tech research when all other options aren’t appealing.

Granted, dedicated resources to parts tech does not help with the immediate strengthening of your APCs, base development or battle so don’t solely depend on upgrading this tech otherwise you may find your overall growth moving at a slower pace. That and you need energy cores which are a prerequisite to doing these upgrades… so don’t find yourself out of inventory when you need it.

Keep Producing Energy Cores

In order to have parts research as your backup to your main research upgrades, you should have a healthy stock of energy cores produced at all times. The parts research themselves do help make crafting APC materials and parts faster, so it’s worthwhile investing in parts research on the side.

Every parts research requires energy cores and as you get to the higher levels they require much more. This can make it difficult to upgrade the parts factory which offers better return to faster production than the research tech does, but needs a huge amount. So you should plan ahead always produce all the time.

Balance the level of your energy refining plants so you can refill them all at the same time. This requires large amounts of electricity and you can save enough by following my guide on the fastest way to save electricity (opens a new window).

Hourly Research Rewards

Once you’ve finished your 50% or 100% COZ Ticket (Always recommend exchange 4 green COZ tickets for a 100% ticket), don’t stop there. Help your next research upgrades later in the day by doing hourly challenges that reward research speedups in the chests.

Usually, the third hourly chest requires the most resources so a rule of thumb is to only hit the second purple chest. You’ll get research speedups, net positive diamonds, and resources to help land your next research upgrade. They don’t always come around so if you do an hourly, check the chest rewards to make sure.

Spend VIP Points


If you already have or recently unlocked the paid VIP Shop option, you may not realise that VIP Points actually give you a high level of COZ Points. You get +8 per every VIP Point spent – which can be accrued through completing daily tasks, exchanging diamonds of spending real cash – and if you time this for tech day, which is usually quite a tough COZ event to hit all 9 chests, you’ll get a nice bump on your hourly challenge and COZ points.

Let’s take VIP Shop level 1 for example – the lowest buff is 250K VIP points for your troops. With maxed zone commemoration, you get 8M COZ points and that’s without a 50% or 100% ticket. The base amount you get for that is the same as what you get for the hourly challenge, which is 2M, which can help you get your third hourly chest.

By calculation that’s (Spend VIP Value * No. of VIP Points Spent) = 8 * 250K = 2M base points. Alternatively, the resources packs give you 80K points. These are best used for the high-value buffs but if you need fillers without burning through speedups, resources, and diamonds, spend those VIP points… that is, if you unlocked the VIP Shop.

Keep an eye out as I will update this once I have upgraded my base and maxed these tech upgrades, offering the best insight into the Elite tech skill trees, defensive queues etc you can expect as you progress in your development. For now, these are the best tips to help you do well on Last Shelter Clash of Zones Research Day!