Cranial Master

Fractured Divinity. The Cranial Master’s soul is fragmented. His full power is sealed in a Reality Gem embedded in the Astral Throne. As a result, he: Cannot use reality-warping powers unless near the Throne (see Reality Warp). Regains 10 HP at the start of each of his turns while within 60 feet of the Throne. Takes double damage from spells or attacks originating from the gem.

Psionic Overmind. The Cranial Master can maintain concentration on two powers at once. He rolls concentration checks separately for each.

Mindweaver Form. His body resembles a massive spider made of intertwining brain matter and psychic sinew. He can move through spaces as small as 1 foot wide without squeezing. He can climb on walls and ceilings without a check. Creatures who end their turn within 5 feet of him must succeed a DC 18 Wisdom saving throw or have disadvantage on Intelligence, Wisdom, and Charisma saves until the end of their next turn.

Vestige of the Throne. Once per day, if the Cranial Master is reduced to 0 HP, he instead transforms into a phase-shifted form of psionic energy for 1 minute (see Phase Ascendance under Bonus Actions). This transformation restores him to half HP and changes his movement to fly 60 ft. (hover), but he becomes vulnerable to force and radiant damage.

Multiattack.The Cranial Master makes two Psychic Fanglash attacks and uses Mental Collapse if available.

Psychic Fanglash.Melee Spell Attack: +11 to hit, reach 10 ft., one target.
Hit: [roll]4d8+3[/roll] psychic damage. The target must succeed a DC 18 Intelligence saving throw or suffer Mind Bleed: take [roll]1d8[/roll] psychic damage at the start of each turn for 1 minute (save ends).

Mental Collapse (Recharge 5–6).Targets up to 3 creatures within 90 feet. Each must make a DC 18 Intelligence saving throw. On a failure: Take [roll]8d8[/roll] psychic damage. Become Incapacitated until the end of their next turn. On success, take half damage and no additional effect.

Mind Puppet (1/Day).The Cranial Master targets one creature it can see within 60 feet. The creature must succeed a DC 18 Charisma saving throw or become a puppet for 1 minute. While under this effect:The creature takes its turn as normal, but the  Master controls its actions and movement (no save each round). At the end of each of its turns, it can repeat the saving throw, ending the effect on a success.

Phase Ascendance (1/Day). (Triggered at 0 HP) The Cranial Master becomes incorporeal, appearing as a translucent brain-shaped spider made of thought. While in this form: He can move through solid objects. All attacks become force damage. He has resistance to all damage except force and radiant. After 1 minute, he collapses into inert brain matter unless restored by proximity to the Astral Throne.

The Cranial Master can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature’s turn. He regains spent legendary actions at the start of his turn.

1. Echo Command.

Force a creature Charmed or Puppeted by the Cranial Master to take an additional action immediately.

2. Synaptic Surge.

The Cranial Master forces a creature within 60 feet to make a DC 18 Intelligence save or take 13 (3d8) psychic damage and be unable to cast spells until the end of its next turn.

3. Reality Warp (Costs 3 actions).

Only usable within 60 feet of the Astral Throne.
The Cranial Master momentarily channels his former thronebound power, choosing one:

• Reverse Gravity (no concentration)

• Modify Memory (as a lair-wide flash)

• Time Stop (lasts [roll]1d4[/roll] turns, no concentration)

Once used, he cannot use Reality Warp again for 24 hours.