Here is the full list of all 21 Order Of The Gatekeepers achievements.
Deal over a million damage with a single critical hit.
Complete any level on Serious difficulty without taking damage.
Play a match with the game's creator Jordan.
Build any of the lategame items from a Gatekeeper's Artifact.
Make over 200 gold from interest in a single wave.
Take over 125 damage in a single match and still win.
Have at least 10 washing machines present simultaneously.
Watch at least 13 enemies get destroyed by one cast of the Alter of Ker's Cull ability.
Get a Jackpot on your Slot Machine.
Reach level 25 on any Tower.
Reach 15 simultaenous Buffs on any Tower.
Reach wave 125 in Endless Mode.
Save over 300 mana with one use of the Inhibitor.
Obtain over 100% Mana Cost Reduction on any Tower.
Smash at least 15 enemies at once with the Shifter's Earthhammer.
Survive an otherwise deadly enemy due to Life Guardian Self-Sacrifice.
Complete any level on Serious difficulty with the No Wave Delay mutator and no damage taken.
Complete a level on Serious difficulty with the No Buying Items & All Items Drop mutators.
Force enemies to take a path more than 2.5x the length of the original on any Mazing level.
Complete any level with Mazing gameplay on Serious difficulty.
Win a mazing level without changing the path at all.