Spellcasting. yanesal is a 20-level spellcaster. His spellcasting ability is charisma (spell save DC 26, +21 to hit with spell attacks).Yanesal has following spells prepared requiring no material components or rituals

 at will: fireball, burning hands,
once per day: plane shift                                                                                                                    three times per day: power word kill, power word stun.

multiattack. yanesal makes two melee attacks or two spells or one melee and one demonic touch

demogorgans fang(double sided sword). Melee Weapon Attack: +23 to hit, reach 5 ft., 1 target. Hit: 45 (10d6 + 20) slashing damage. 

Demonic touch. Melee Weapon Attack: +23 to hit, reach 5 ft., 1 target. Hit: 45 (5d10 + 20) fire damage. the target must make a dc 28 constitution saving throw or be frightened till the end of yanesals next turn

demogorgans fang(longbow). RangedWeapon Attack: +23 to hit, range 10/1000 ft., 3 targets. Hit: 30 (4d10 + 19) piercing and 25 (3d10 + 15) fire damage.

jump.if an attack hits yanesal can jump up to 40 ft away and do 3d12 fire damage

ray of fire (Costs 2 Actions). 8d8+12 fire damage range 200/500