Critical RollG 20

If you’re attempting this achievement today the only way to acquire the D20 is by buying it from Larinna, who you can find standing outside each Tavern on every Outpost in the game.

The dice don’t come cheap - they’ll cost you 300 doubloons - but it’s a small price to pay for a rare achievement. Once you’ve bought the dice, go to a vanity chest and equip the Roll D20 emote.

Then just select that emote over and over to keep rolling the die. Eventually you’ll roll a 20 and unlock the achievement.