Legendary Resistance (3/Day). If Xyltris fails a saving throw, he can choose to succeed instead.

Accelerated Time: Xyltris has advantage on initiative rolls.

Consumption of Years: Because of Xyltris' many stolen years, he has limited spell immunity, and cannot be effected by spells of 4th level or lower.

Spellcasting. Xyltris is a 20-level spellcaster. His spellcasting ability is [intelligence] (spell save DC 19, +11 to hit with spell attacks). Xyltris has following wizard spells prepared:

Cantrips (at will): [fire bolt], [mind sliver], [chill touch], [sapping sting]

1st level (4 slots): [detect magic], [witch bolt], [magic missile], [gift of alacrity], [magnify gravity]

2nd level (3 slots): [crown of madness], [darkness], [mind spike], [tasha's mind whip], [shadow blade], [fortune's favor], [immovable object]

3rd level (5 slots): [counterspell], [dispel magic], [melf's minute meteors], [lightning bolt], [erupting earth], [pulse wave]

4th level (4 slots): [dimension door], [Raulothim's psychic lance], [Evard's black tentacles], [confusion], [gravity sinkhole]

5th level (3 slots): [synaptic static], [temporal shunt], [enervation]

6th level (2 slots): [gravity fissure], [chain lightning], [disintegrate]

7th level (2 slots): [tether essence], [reverse gravity], [plane shift]

8th level (1 slot): [dark star], [reality break], [feeblemind]

9th level (1 slot): [ravenous void], [time ravage], [time stop]

Swing Staff. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: (2d8 + 5) [bludgeoning] damage + (1d10) [necrotic] damage. 

Enter the description for how bonus actions work for your monster here.

Rewrite Time: After being hit by an attack, Xyltris can use his reaction to cause that creature to reroll the attack with disadvantage.

Xyltris 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. Xyltris regains spent legendary actions at the start of his turn.

Cast a Spell (Costs 1 Action). Xyltris can cast a spell of 4th level or lower.

Reposition The Battlefield (Cost 2 Actions). Xyltris can reposition and move everyone in a 150ft cube using a combination of time and gravity magic. Everyone targeted must make a wisdom saving throw (DC 19), or be shifted to his liking. On a successful save, that creature is unmoved.

Enter the description for how mythic actions work for your monster here.

Mythic Action Name (Costs # Actions). Enter the description for your mythic action.