O Assistente da Escola de Necromancia possui o recurso Command Undead (PHB, p. 119):
Starting at 14th level, you can use magic to bring undead under your control, even those created by other wizards. As an action, you can choose one undead that you can see within 60 feet of you. That creature must make a Charisma saving throw against your wizard spell save DC. If it succeeds, you can't use this feature on it again. If it fails, it becomes friendly to you and obeys your commands until you use this feature again.
Intelligent undead are harder to control in this way. If the target has an Intelligence of 8 or higher, it has advantage on the saving throw. If it fails the saving throw and has an Intelligence of 12 or higher, it can repeat the saving throw at the end of every hour until it succeeds and breaks free.
O Nightwalker de Tomo dos inimigos de Mordenkainen (p. 216) possui carisma de 8, inteligência de 6 e um CR de 20.
Não é um pouco louco? Além de simplesmente não colocar essa coisa no jogo se você tiver um assistente de necromancia, o que mais pode acontecer (ou o Mestre pode fazer) que impedirá o jogo de quebrar?