Oppose the Foes Is Now Available in the Vaults of Atal'Utek

Week three of Patch 12.1 has unlocked Oppose the Foes for anyone who has been keeping up with the Vaults of Atal'Utek. It is a straightforward achievement with one genuinely annoying property: you cannot rush it, and if you have already missed a week, you are waiting.

It also feeds into a meta with a mount at the end of it, which is the real reason to care.

What the achievement asks for

You need to defeat all three Ancient Foes in the Vaults of Atal'Utek: Congealed Malice, Khu'tulak and Susarikk.

Finding them is easy. Ancient Foes become available directly after you kill a Temple Incursion, and they show up on your minimap once they are up. No hunting required.

This is the catch. The three bosses rotate, one per week, which makes three weeks the absolute minimum for this achievement. There is no way to compress it and no alternative route.

And if you skipped a week — say you were busy with the Season 2 opening and did not touch the Vaults — you do not get to catch up. You wait until that specific boss cycles back into the rotation. For anyone who came to Patch 12.1 late, this is one of the achievements that quietly puts you weeks behind.

The drops are worth the trip anyway

Even ignoring the achievement, Ancient Foes are worth tagging. They drop Corrosive Coin, and on your first kill of the week they also drop a Corrosive Soul and a Venom-Cursed Fragment.

Repeat kills within the same week still drop the Venom-Drenched Sack, so there is no reason to stop after one. Corrosive Souls in particular are the currency behind Corrosive Codex powers, and those are slow enough to accumulate that every guaranteed source counts.

Where it leads: Assault the Vault

Oppose the Foes is one of several achievements feeding the Assault the Vault meta, which rewards the Venomous Coiler. That is the actual prize here — the achievement on its own is a tick in a list, but the meta is a mount.

Because the rotation is fixed, the sensible approach is to start now regardless of what else you have completed. Every week you delay is a week added to the back end, and there is no version of this where you catch up quickly.