Baron Ivald One-Eye

Rage of the Arisen: When Ivald One-Eye is reduced to 25% HP or less, he automatically gains the benefits of Rage, Frenzy, and Reckless attack until he is defeated. This is done without a bonus action.

Undead Fortitude: If damage reduces Ivald to 0 hit points, he will make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, Ivald regenerates 2d10+5 HP. 

Death Song: Any foe killed by Ivald is resurrected as a thrall commanded by Ivald, with stats determined as detailed in Deathsong's unique weapon sheet.

Call of the Legion: As a bonus action, Ivald can enlist the aid of 1d8 Undead Warriors. This action can be taken until a total of 8 undead allies have been summoned.

Vicious Slash: Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 10 (1d12+4), slashing damage and 2 (1d4) necrotic damage.

Sundering Cleave: Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 10(1d12+4) slashing damage, 7(1d6+4) bludgeoning damage, and 2(1d4) necrotic damage. Target must make a Constitution saving throw, DC:15. If failed, the target is now stunned.