Lets say that the DM throws his super monster at you and it happens to be a Tarrasque. From what I was looking at it never really tells you what plane of existence they come from so in theory could you use banishment on it and just send it away to another plane of existence for them to deal with.
Does anyone know what plane the Tarrasque comes from, and can I use banishment on it for the full duration to banish it permanently?
Best Answer
You can try, but success is short lived (and you may be, too)
The Tarrasque (MM, 286) is a:
Because of that, Banishment (Basic Rules, 217) can work, but you'll only have a minute until it comes back if you're fighting it on its home turf.
Good chance it makes the save
But that's if it fails the save at all.
The Tarrasque has advantage on saves against magical effects, it has three uses of Legendary Resistance daily and can choose to make the save, and it's still got a +9 modifier to Charisma saves. Odds are it's making that save.