Magic Resistance. Zelathor has advantage on saving throws against spells and other magical effects.

Consume Mind. Zelathor can feed off of the minds of unconscious creatures and heal 10 hp per +1 intelligence modifier of prey. this rarely kills the creature, but they often have a large hole at the base of the skull in the nape of the neck.

Portray Form. Zelathor has no physical form. It projects an image of itself into the minds of those aware of it. Often taking the form of a massive brain with tentacles and a mouth with long needle-like inward facing teeth along with one cyclopic immense eye with a purple iris and a white slit shaped pupil that stares intensely. similar to that of an aboleth.

-----Frightening Appearance. when other creatures see this Portray-ed Form, they  must make a wisdom saving throw (DC 20) or be frightened for 10 minutes.

Multiattack. Zelathor can use Teleport. It then takes seven actions: one with its Snatch, two with its Compress, two with its Ravage Mind, and two with its Push. 

Snatch. Ranged Spell Attack: +19 to hit, reach 120 ft., up to two targets of less than or equal to 500 lbs. each. Hit: 20 (3d6 + 8) force damage and the two targets slam together 6 per 5 ft. plus 10 (2d4 per 5 ft. + 10) bludgeoning damage and are moved and held 30 ft. up and up to 30 ft. closer to Zelathor. If the target is a creature, it is grappled (escape DC 20). Until this grapple ends, the target is restrained.

Compress. Ranged Spell Attack: +19 to hit, reach 30 ft., one Snatched target. Hit: 45 (4d10 + 10) force damage. End grappled

Ravage Mind. Ranged Spell Attack: +19 to hit, reach 15 ft., one target. Hit: 45 (5d10 + 10) psychic damage.

Push. Ranged Spell Attack: +19 to hit, reach 60 ft., one target. Hit: 26 (4d6 + 10) force damage. If the target is a creature, it must succeed on a DC 20 Strength saving throw or be pushed 30 ft. away from Zelathor and be knocked prone.

Teleport. Zelathor teleports anywhere within 90 feet of its position before teleportation.

Enslave (3/day): Zelathor targets one creature it can see within 30 ft. of it. The target must succeed on a DC 15 Wisdom saving throw or be magically charmed by Zelathor until either dies. The charmed target is under Zelathor's control and can't take reactions, and they can communicate telepathically with each other over any distance. Whenever the charmed target takes damage, the target can repeat the saving throw. On a success, the effect ends. No more than once every 24 hours, the target can also repeat the saving throw when it is at least 1 mile away from Zelathor.

If Zelathor takes 50 damage or more on a single turn, it must succeed on a DC 20 Constitution saving throw at the end of that turn or release all grappled creatures, which fall prone straight down with appropriate fall damage. If Zelathor dies, it releases all creatures restrained by it which are dropped prone (with appropriate fall damage).

Deflect. when hit with a ranged spell that deals damage, roll 1d20. On a 10 or lower the spell is deflected back at the original caster. If you roll 11 to 15, the spell has no effect. anything else is unaffected by this reaction.

Teleport. when hit with a melee attack, use the Teleport action. the attack misses.

Zelathor 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. Zelathor regains spent legendary actions at the start of its turn.

Shift. Creates a mirror image of itself centered no further than 10 ft. off of Zelathor's center. Imposes disadvantage on offensive actions targeting Zelathor that rely on sight

Disappear. Zelathor stops projecting its image upon others minds rendering completely invisible to anything except those whom can see into the ethereal plane.

Lash Out (Costs 2 Actions). All creatures within 60 ft. make a wisdom saving throw. Taking 42 (4d12 + 10) psychic damage on a failure and half of that on a success.