Multiattack. The grave knight maks two greatsword attacks. It can use its Life Drain in place of one greatsword attack.

Life Drain. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 4) necrotic damage. The target must succeed on a DC 13 Constitution saving throw or its hit point maximum is reduced by an amount equal to the damage taken. This reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.

+2 Greatsword. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 6) slashing damage.

Zagren can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. Zagren regains spent legendary actions at the start of its turn.

+2 Greatsword. Zagren makes one +2 Greatsword attack.

Summon skeleton minions (Costs 2 Actions). Zagren summons 1d4 skeleton minions. The skeleton appear within 30 feet of Zagren.