My group got Cold Potato on PS/NA in January 2025.

We had trouble getting this achievement, because it was difficult to find all the information we needed to satisfy the conditions of the achievement.

The wording is weird and misleading.
"Cold Potato is awarded for defeating Rizzuk and Avalanche in Veteran Frostvault with each party member having been affected by Avalanche's Glacial Prison ability at least once."

It should say something more like:
"Each party member must simultaneously have the debuff given by the Glacial Prison Ability before defeating Rizzuk and Avalanche."

The achievement requires:

• Has to be done on Vet Frostvault
• Has to be done with 4 players, not 3 and a companion, or fewer.
• Each player has to get the debuff from being hit by the potato. However, the potato will choose who to target randomly, and may not target all four people, SO:
  • The first person targeted by the Potato must get hit and get the debuff. If a person without the target picks up the debuff first, the achievement won't trigger.
  • After the first targeted player gets debuffed, anyone, even if not targeted, can get hit by the potato and be debuffed. The person with the target can lead the potato towards whoever needs the debuff next.
  • The debuff goes away if a person dies.
  • A person can get the debuff again after they die and rez and the achievement will still work. But all 4 players must be debuffed simultaneously.
  • The debuff lasts 10 minutes, so the main time issue can be killing the bosses too fast.
• If the group wipes, it can start again, but it gets buggier the longer the fight goes on.
• It's unclear what happens if the first person debuffed dies. Can they get the debuff again? Or does the fight have to start over? We didn't encounter this.

The debuff icon looks like this:


Being targeted looks like this (standard targeting circle under your feet):

(screenshot from "ESO Frostvault Achievement: "Cold Potato")

The Potato (Glacial Prison) looks like this:

(screenshot from "Cold Potato Achievement - Super Easy Guide - Frostvaults")

Other notes:
When we did this in early '25, we could wipe on the Rizzek fight and we wouldn't have to start over. Maybe we simply didn't encounter the bug mentioned here.

Sources:
Xynode's guide: (Start here!)
Cold Potato Achievement - Super Easy Guide - Frostvaults (Youtube)
ESO Frostvault Achievement: "Cold Potato" (Youtube)
Cold Potato Achievement Guide (Forums)

ZoS: I know this should be under "Player Guides." I can't create a new post there. Feel free to move it. This is mostly here for Google and future searchers.

Google Bait:
#Frostvault #ColdPotato #Achievements "cold potato" "cold potato achievement" #Wrathstone #WrathstoneAchievements "Wrathstone Achievements"

Editing rights reserved, will try to mark as best I can given the limits of the forums.