Here is the full list of all 11 Gatedelvers achievements.
Reach a fountain.
Kill a boss.
Unlock 6 decks.
Unlock 12 decks.
Die 100 times.
Kill an elite boss.
Reach a deeper fountain.
Pick up a legendary item.
Pick up a pure item.
Apply 3 infusions to an item.
Apply 4 infusions to an item.