Here is the full list of all 20 Tomb of Tyrants achievements.
Fulfill 75 prophecies (cross-session).
Acquire 5 corrupted heroes at once.
Kill a hero with your Tyrant.
Fulfill 50 prophecies (cross-session).
Defend a floor with three max-level minions in one battle.
Reach wave 25.
Complete 20 plots in a single session.
Fulfill 25 prophecies (cross-session).
Earn a level 10 minion.
Earn 10 level-5 minions in a single session.
Construct a 20-floor dungeon.
Achieve a 5x multiplier.
Reach wave 10 without spending resources on minions.
Reach wave 10.
Use 20 potions in a single session.
Complete 30 rituals in a single session.
Stockpile 50 of a single resource at one time.
Construct a 10-floor dungeon.
Without using items, achieve a 2x multiplier on a single resource match.
Achieve a 3x multiplier.