Life Siphon. When the red knight reduces a creature to 0 hit points, the creature suffers disadvantage on any death saving throws and the red knight can use its reaction to cast a spell it has prepared.

Purging Touch (4/day). As an action, the red knight can end one spell on itself or on one willing creature that it can touch.

Divine Smite. As a bonus action, the red knight can expend a spell slot to cause its melee weapon attacks to magically deal an extra 9 (2d8) radiant damage to a target on a hit. This benefit lasts until the end of the turn. If the red knight expends a spell slot of 2nd level or higher, the extra damage increases by 1d8 for each level above 1st. The damage increases by 1d8 if the target is an undead or a fiend.

Aura of Blood. The red knight, as well any fiends, undead, and any other creature friendly to it within 10 feet of the red knight, gains a bonus to melee weapon damage rolls equal to the red knight’s Charisma modifier (minimum of +1). A creature can benefit from this feature from only one red knight at a time.

Regeneration. The red knight holds power over the flow of its own blood and the speed at which it heals. The red knight regains 15 hp at the start of its turn if it has at least 1 hp.

Spellcasting. The red knight is a 15th-level paladin. Its casting ability is Intelligence (spell save DC 17, +9 to hit with spell attacks). It has the following paladin spells prepared:

1st level (4 slots): command, false life, hellish rebuke, inflict wounds, wrathful smite

2nd level (3 slots): crown of madness, hold person, darkness, branding smite, lesser restoration

3rd level (2 slots): dispel magic, revivify, animate dead, vampiric touch, bestow curse

4th level (2 slots): blight, confusion, staggering smite, banishment

Multiattack. The red knight makes two greatsword attacks.

Greatsword. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 16 (2d6 + 5) slashing damage plus 7 (2d6) necrotic damage plus 4(1d8) radiant damage.

Blood Magic (Recharge 5-6). The red knight uses one of the following:

• Impale. The red knight causes 10-foot spikes made of blood to burst from the ground within a 15-foot radius it can see within 30 feet. Each creature in the area must make a DC 16 Dexterity saving throw, taking 26 (4d12) piercing damage plus 7 (2d6) cold damage on a failed save, or half as much damage on a successful one.
• Drown. The red knight sends blood pouring down the throat of one creature within 30 feet, which must make a DC 16 Constitution saving throw. On a failure, the creature is incapacitated until the end of its next turn as it coughs up the blood and is poisoned for 1 minute after that.
• Vaporize. A red mist surrounds the red knight in a 20-foot-radius sphere. The mist spreads around corners, and its area is heavily obscured. It moves with the red knight and doesn’t impede the red knights' vision. The mist dissipates after 1d4 rounds.