The best Aetherium Crystals upgrades in Black Ops Cold War Zombies

Keep getting clobbered by zombies even when you've chugged down a Juggernog? Want to make your loadout even stronger? Need to keep reviving your puny teammate? Well, Aetherium Crystals may be the solution to all of the above in Call of Duty: Black Ops Cold War zombies.

Aetherium Crystals are a new currency in the Call of Duty zombies mode and give players a chance to upgrade their weapons, ammo mods, perks, and field upgrades to give them more of an advantage against the hordes. Effectively, it's a way to make the best zombies loadout even better. Thanks to an update to the upgrade system back in Season 2, each class of weapon, ammo mag, perk, and field upgrade has five stages to upgrade to.

Season Two also introduced two new types of Aetherium Crystals – Refined and Flawless – which are used to upgrade your gear to tiers four and five, respectively. To fully max out everything you possibly can in Black Ops Cold War Zombies, you will need 168 Raw Aetherium Crystals, 112 Refined Aetherium Crystals, and 140 Flawless Crystals. This is the maximum amount you can earn of each type, so once you hit that limit, you'll stop earning them in-game.

Aetherium Crystals aren't easy to come by though, and getting them – particularly the high-rarity ones – can be tough. So how do you earn them, what upgrades are there, and if you haven't got the time to grind and earn all of them, where should you invest your Aetherium Crystals?

How to get Aetherium Crystals in Black Ops Cold War Zombies

Here's how to earn each type of Aetherium Crystal, and how they're used to upgrade your loadout.

Raw Aetherium Crystals

There are currently three ways to earn regular Aetherium Crystals in Black Ops Cold War zombies.

The first is to complete milestone rounds during a Zombies run on Die Maschine and Firebase Z. These milestone rounds are every five rounds from round ten onwards. The amount of crystals you earn for each milestone round does vary, so here's a chart showing you how many you're expected to get at the end of each milestone round.

Note that the amount can sometimes fluctuate from the figures shown in the chart above and there are instances of players getting one extra or one less crystal than expected when completing a milestone round.

The crystals also stack as you go through a Zombies run, so if you reach round 21 for example, you would have earned three crystals in total for hitting milestones at 10, 15, and 20.

The second method is through exfils, which allow you to end your Zombies run by jumping aboard a chopper and leaving the undead behind.

Similarly to milestone rounds, you will be awarded a certain amount of crystals depending on which round you exfil on. For example, a round 31 exfil should award you two crystals, as you have passed the round 30 milestone. However, exfil crystal drop rates have been found to be a bit more random and can sometimes drop far below what you expected.

Another method to earn crystals is through completing the Die Maschine easter egg. However, this is very time-consuming, so isn't an efficient way to grind for crystals.

Finally, raw Aetherium Crystals will also drop for each round you complete in the Outbreak Zombies mode, which was added back in Season 2. We have more on how many you can earn further down this guide.

Refined Aetherium Crystals and Flawless Aetherium Crystals

Upgrading a piece of gear in Black Ops Cold War zombies to Tier 4 will set you back four Refined crystals, and upgrading to Tier 5 will cost five Flawless crystals. So how do you get them?

Refined and Flawless crystals can drop at high rounds in existing Zombies maps Die Maschine and Firebase Z.

However, along with the Raw crystals, Refined and Flawless Aetherium Crystals will also drop at the end of high rounds of Outbreak. We saw slight variations in drop rates from our playthroughs, but you can see our findings below.

Outbreak Aetherium Crystal Rewards

At the end of each completed round of Outbreak, you will receive some Aetherium Crystals. The higher the round, the more of each type you will get.

This isn't an exact science, and after comparing our drop rates with that of Zombies streamers at the time, the amount of crystals you get can vary. However, below is a table showing the rough formula:

How do I spend Aetherium Crystals in Black Ops Cold War zombies?

Aetherium Crystals can be used to upgrade everything in your best zombies loadout in Black Ops Cold War. To see what upgrades you can spend your crystals on, go to the loadout tab in the Zombies lobby menu, then to skills, and then to one of the four categories of upgrades: weapon classes, field upgrades, perks, or ammo mods.

Each upgradeable item or class has five upgrade tiers. The table below shows how many of each crystal you need to upgrade a piece of gear to each tier.

To fully upgrade everything in Black Ops Cold War Zombies, you will need 168 Raw, 112 Refined, and 140 Flawless crystals.

Best Aetherium Crystals weapon class upgrades

Each class of weapon in Black Ops Cold War can be upgraded using Aetherium Crystals to help you in Zombies runs.

Most of the upgrades are quite similar, ranging from damage increases to unlocking extra attachment slots for some classes of weapons. If you're looking to make the best Cold War Zombies weapons even better, we recommend investing crystals into the shotgun, melee, and assault rifle classes first.

Note that like in multiplayer, weapon classes will unlock and be available for upgrades at certain player levels. The final weapon class, melee, is unlocked at level 50.

Best Aetherium Crystals field upgrade upgrades

As well as tweaking your guns, you can also upgrade the six zombies-specific field upgrades in Black Ops Cold War: Frenzied Guard, Frost Blast, Energy Mine, Aether Shroud, Healing Aura, and Ring of Fire.

While many of the weapon class upgrades were quite similar across the board, Aetherium Crystals can be used to radically change your field upgrades in a number of ways. For those looking to go on long, high-round runs, we recommend maxing out either Aether Shroud for getting out of tricky spots or Ring of Fire to help take down the tanky bosses.

Best Aetherium Crystals perk upgrades

The seven currently available perks in Black Ops Cold War zombies can all be upgraded to be even more useful with your Aetherium Crystals.

While every perk has its uses, the upgrades on offer for Juggernog and Stamin-Up are ones you should definitely pay close attention to.

A fully upgraded Juggernog will see your max health increase by 100 and will allow you to pick up more armour when you find it as ground loot. Meanwhile, a maxed-out Stamin-Up can allow you to sprint for pretty much unlimited time, all while using your weapons or field upgrades.

Aetherium Crystals ammo mod upgrades

Ammo mods can be super useful in Black Ops Cold War zombies to give your favourite weapon an extra kick. Using Aetherium Crystals, you can make their effects even more powerful by upgrading them.

The specific upgrades are fairly self-explanatory – they essentially make the benefit of having the ammo mod far stronger or last for a longer period of time.

If you have a favourite go-to ammo mod, you should definitely spend some crystals on making it much stronger. However, if you're low on crystals, you should definitely invest them in upgrading weapon classes, perks, and field upgrades first in our humble opinion.

That's all you need to know about Black Ops Cold War Zombies Aetherium Crystals, whether you're jogging your memory from years away or finally giving it a go for the first time. While they can be hard to come by, grinding Outbreak is definitely the way forward to give your gear a real boost.