Chelonian Gate

Conjures a 'Chelonian Gate' for 2 rounds, decreasing damage taken by 20%. If you move or take another action, bonus action or reaction, the 'Chelonian Gate' disappears. If you take damage equal to 30% of your max HP, you can use your reaction to cast 'Divine Cataract'. 'Divine Cataract' can be cast with a reaction at any point, so long as the 'Chelonian Gate' is active.

'Divine Cataract' unleashes a wave around you. All creatures within 25 feet of you must make a STR saving throw or take 5d6 force damage, with the closest creature taking 10d6 force damage instead. If your AC is 18 or higher, the damage is doubled. Creatures take half damage on a successful save.