Excal-heim
Undead Fortitude. If damage reduces the sun knight to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is from a critical hit.
On a success, the skeletal knight drops to 1 hit point instead.
If the sun knight's armor is broken or removed, bludgeoning and radiant damage will also prevent its undead fortitude.
Unusual Nature. The sun knight doesn't require air, food, drink, or sleep.
Sol-rai's helm. The sun knight's armor is magical, granting them immunity to turn undead, radiant damage, and magic that detects undead.
Drops: Rapier of dawn
Multiattack. Sun knight makes three melee attacks.
Rapier of dawn. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 8 1d8+4 radiant damage.
Upon dealing max holy damage, the target becomes blinded until the start of their next turn.
Spellcasting. Sun knight casts one of the following spells, using Charisma as the spellcasting ability (spell save DC 14):
Protect Another. When a creature the sun knight can see attacks another creature that is within 5 feet of him, they can impose disadvantage on the attack roll, provided the sun knight is carrying a shield.