Exalted Restoration. If it dies away from its home plane, its body vanishes and it re-forms there with all its Hit Points.
Magic Resistance. Advantage on saving throws against spells and other magical effects.
Actions
Multiattack. Makes two Holy Mace attacks.
Holy Mace. A mace blow carrying a burst of radiant power.
Spellcasting. It casts with Charisma (save DC 17), needing no Material components. At will: Detect Evil and Good, and Shapechange limited to Beast or Humanoid forms, without Concentration and without the spell's Temporary Hit Points. 1/day each: Commune, Raise Dead.
Bonus actions
Divine Aid. Uses the same spellcasting ability as its Spellcasting action. The two uses cover all three spells.
Where you meet it
The Church of St. Markovia: The candles go white. He doesn't draw a weapon. He opens his hands, and there is suddenly a mace of light in…