Mahoraga

Magic Resistance. Mahoraga has Advantage on saving throws against spells and other magical effects.

Adaptation. If an attack is used against Mahoraga, in 2 turns time they will become immune to that attack and be completely unaffected by it from then on. If another creature uses the same attack, Mahoraga will be immune to that too (eg. a tiger using a claw attack will make Mahoraga immune against any other creatures with that attack). If a creature is immune or resistant to an attack in Mahoraga's vicinity, in 2 turns Mahoraga will ignore those immunities and resistances with attacks they or their summon make.

Multiattack. Mahoraga makes three slashing attacks using the sword of extermination.

Sword of Extermination. Melee Attack Roll: +10, reach 10 ft. Hit: 16 (2d10 + 5) Slashing damage plus 11 (2d10) Force damage.

Horror Nimbus (Recharge 5–6). Wisdom Saving Throw: DC 15, each creature in a 15-foot Emanation originating from Mahoraga. Failure: 28 (8d6) Psychic damage, and the target has the Frightened condition for 1 minute, until it takes damage, or until it ends its turn with the nalfeshnee out of line of sight. Success: The target is immune to Mahoraga's Horror Nimbus for 24 hours.

Pursuit. Trigger: Another creature that mahoraga can see ends its move within 120 feet of the nalfeshnee. Response: Mahoraga uses Teleport, but its destination space must be within 10 feet of the triggering creature.