At 18th level, you gain one of the following features of your choice:
Armor of the Liondillo. You can spend 1 ki point as a reaction whenever you are attacked. Until the beginning of your next turn, you have resistance against the type of damage that harmed you, including against the triggering attack
If the triggering attack deals more than one damage type, you gain resistance to both types of damage until the beginning of your next turn.
Jaws of the Whiskergator. You can spend 3 ki points on your turn. Until the beginning of your next turn, the damage of your elemental strike (but not any additional features, such as Prana Burst) deal their maximum damage.
Rise of the Phoenix. You can spend 1 ki point any time you are reduced to 0 hit points but not killed outright to drop to 1 hit point instead.
Each time you use this ability, it costs 1 additional ki point. When you complete a long rest, the cost resets to 1 ki point.