Spellcasting. Yvraine is a 10-level spellcaster. Its spellcasting ability is [ability score] (spell save DC 30, +5 to hit with spell attacks). Yvraine has following Sorcerer spells prepared:
Cantrips (at will): Sacred Flame, Bane, Command, Cure Woulds, Detect Evil and Good, Healing Word
9st level (20 slots): Mass Heal, Holy Aura, Invulnerability, Power Word Death. 

Multiattack. Yvraine can use its Presence. It then makes 3 attacks: three with its divine sword.

Divine Sword Attack. Melee Weapon Attack: +15 to hit, reach 7 ft., 3 target. Hit: 45 (3d12 + 30) [slashing, fire and radiant] damage. 

Bonus action. Fly without taking attack of opportunity 60 feet

Opportunity Attack. You can make an Opportunity Attack when a hostile creature that you can see moves out of your reach. To make the Opportunity  Attack you use your reaction to make one melee Attack against the provoking creature. The Attack occurs right before the creature leaves your reach

Yvraine 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.

Word of the Phoenix (Costs 1 Actions). Yvraine can call upon the power of Ynnead to restore life to a nearby fallen warrior, resurrecting Eldar allies on the battlefield.

Gaze of Ynnead (Costs 3 Actions). She channels Ynnead's power into psychic blasts that deal 5D 12 psychic damage to enemies, especially effective against beings with souls. It's a devastating skill in combat.