1. Permanent antimagic field, and
2. Resistance to nonmagical weapons, and
3. Ability to inflict exhaustion with every attack based on an Intelligence save, and
4. Multiattack with at least 3 and preferably 5 or more attacks, and
5. Ability to inflict disadvantage on saving throws as an AoE effect.
That's all you need to be either maximally anti-player or damn close to it. The permanent antimagic field plus nonmagical weapon resistance guarantees very little will even be able to attempt to damage you. Then the combo of inflicting exhaustion on a save with every attack you make, making tons of attacks, and inflicting disadvantage on saves to more than one target at a time? Yeah, you've basically guaranteed you'll destroy most PCs within a few rounds. With 5 attacks, it's theoretically possible (probable, even, if that disadvantage applies) to have someone on the verge of death by exhaustion after a single round.