Please welcome Theggex, a fledgling of undeath, a newborn amongst the lich, once an Illithid, now a ProtoIllithilich as its way to becoming one of the most fearsome entities to stalk the realms. Theggex isn't at full power however-- but that's fine, adventurers have already witnessed his rebirth. Who would be better to test his powers against? Possessing devastating attacks, the adventurers are in HIS realm, HE controls everything! As a Lair Action, he can choose which cells in his room actively have anti-magic and leave himself nearly invulnerable to all attacks. Can you figure out how to bypass these squares? Or is merely surviving all you can accomplish. Please do grapple him, Theggex will feast on your brains more easily that way... SLURP!!!
Wait-- your brains were extracted and you're alive? In fact, Theggex just called for a time out? What in the nine hells? Sorry, if you are killed in Theggex's realm he isn't eager to have you die. No, you're out of the fight for three rounds so you need to go sit against the wall and then you'll be allowed to join again. What twisted game is this? He's toying with you and when he feels enough damage has been received the fight ends-- and you're thanked!?
Picture: James Grieves (https://es.pinterest.com/pin/535224736982881707/)