Baba Yaga's Horsemen, Red Sun

the horseman is a 12th-level spellcaster. Its spellcasting ability is Charisma (save DC 16, +8 to hit with spell attacks). It can innately cast the following spells, requiring no material components:

1/day each: dimension door, fire shield, haste, slow

2/day each: continual flame, scorching ray

3/day each: ethereal jaunt, phantom steed (appears as a horse colored appropriately to the horseman), plane shift (self and steed only)

The horseman has advantage on saving throws against spells and other magical effects.

Any attacks directed at the horseman's mount targets the horseman instead. Its mount gains the benefit of the rider's damage and condition immunities, and if the horseman passes a saving throw against an area effect, the mount takes no damage.

The horseman can switch between wielding its lance and longsword as a bonus action.

Melee Weapon Attack: +10 to hit, reach 10 ft. (disadvantage within 5 ft.), one target. Hit: 12 (1d12 + 6) piercing damage.

Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 10 (1d8 + 6) slashing damage.

The horseman makes three attacks with its lance or longsword. It can use Temporal Strike with one of these attacks when it is available.

When the horseman strikes a target with a melee attack, in addition to taking normal damage, the target must succeed on a DC 17 Constitution saving throw or instantly age 3d10 years. A creature that ages this way has disadvantage on attack rolls, ability checks, and saving throws based on Strength, Dexterity, and Constitution until the aging is reversed. A creature that ages beyond its lifespan dies immediately. The aging reverses automatically after 24 hours, or it can be reversed magically by greater restoration or comparable magic. A creature that succeeds on the save is immune to the temporal strike effect for 24 hours.