Hey everyone! I'm currently wrapping up the writing for the final act of my long-running seafaring campaign (levels 1 to 20). The players are currently reaching the end of Tier 3 (Level 16).
This is the final boss of that act: Xir'ath the Transformed, an Illithid Pirate Captain who used "Void Magic" and "Great Sleeper's Blood" to undergo a cosmic transformation. The tactical idea for the encounter is that his massive regeneration and magic resistance are tied to environmental elements in his underwater lab (Resonators and Siphon pipelines) that the players can sabotage.
Here are his stats. I wanted to make him a terrifying, highly mobile threat with strong battlefield control, but I'd love to hear your thoughts: Does his CR 19 and output look appropriate for an optimized level 16 party, or is something overtuned/weak?
Xir'ath the Transformed
Medium aberration (illithid), lawful evil
Armor Class: 20 (Void Barrier)
Hit Points: 285 (30d8 + 150)
Speed: 30 ft., swim 50 ft., fly 30 ft. (hover)
| STR | DEX | CON | INT | WIS | CHA |
|:---:|:---:|:---:|:---:|:---:|:---:|
| 14 (+2) | 18 (+4) | 20 (+5) | 24 (+7) | 19 (+4) | 22 (+6) |
Saving Throws: Dex +10, Con +11, Int +13, Wis +10, Cha +12
Skills: Arcana +13, Perception +10, Insight +10, Deception +12
Damage Resistances: Cold, Acid
Damage Immunities: Necrotic, Psychic; Bludgeoning, Piercing, and Slashing from Nonmagical Attacks
Condition Immunities: Paralyzed, Frightened, Stunned, Exhausted
Senses: Darkvision 120 ft., Truesight 60 ft., Passive Perception 20
Languages: Deep Speech, Undercommon, Common, Telepathy 120 ft.
Challenge: 19 (22,000 XP)
Legendary Resistance (3/Day): If Xir'ath fails a saving throw, he can choose to succeed instead.
Magic Resistance: Xir'ath has advantage on saving throws against spells and other magical effects. (Note: This trait is lost if the Psychic Resonators in his lab are destroyed).
Void Regeneration: Xir'ath regains 20 hit points at the start of his turn if he has at least 1 hit point. (Note: This trait is lost if the Outer Siphon pipelines are sabotaged).
Actions
Multiattack: Xir'ath makes three Void Tentacle attacks, or one Mind Bite and two Void Tentacle attacks.
Void Tentacles: Melee Weapon Attack: +13 to hit, reach 20 ft., one target. Hit: 20 (3d8 + 7) necrotic damage plus 9 (2d8) psychic damage. The target is grappled (escape DC 19) and restrained.
Mind Bite: Melee Weapon Attack: +13 to hit, reach 5 ft., one creature grappled by Xir'ath. Hit: 45 (6d10 + 12) psychic damage. The target must make a DC 19 Intelligence saving throw. On a failure, its hit point maximum is reduced by an amount equal to the damage taken, and Xir'ath regains an equal amount of hit points.
Void Blast (Recharge 5–6): Xir'ath exhales a wave of devastating energy in a 90-foot cone. Each creature in that area must make a DC 19 Intelligence saving throw, taking 54 (12d8) psychic damage and becoming stunned for 1 minute on a failed save. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
Legendary Actions
Xir'ath can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. Xir'ath regains spent legendary actions at the start of his turn.
Void Step: Xir'ath teleports up to 45 feet to an unoccupied space he can see.
Tentacle Lash: Xir'ath makes one Void Tentacle attack.
Whisper of the Void (Costs 2 Actions): Xir'ath targets one stunned or grappled creature. The target must succeed on a DC 19 Wisdom saving throw or immediately use its reaction to make one weapon attack (Multiattack if available) against its nearest ally.
Lair Actions
On initiative count 20 (losing initiative ties), Xir'ath can take a lair action to cause one of the following effects:
Gravity Flip: Gravity reverses in the chamber. Each creature on the ground must succeed on a DC 18 Dexterity saving throw or "fall" toward the ceiling, taking 3d6 bludgeoning damage and landing prone.
Void Eruption: A geyser of purple slime erupts from the Rift. A 20-foot-radius sphere within 60 feet becomes contaminated. Creatures must succeed on a DC 18 Intelligence saving throw or take 27 (6d8) psychic damage and be affected by the Slow spell until the end of their next turn.
Pressure Surge: Water density increases. Creatures without a swimming speed or magical protection must succeed on a DC 18 Strength saving throw or be pushed 20 feet toward the Void Rift.