All you need to surpass it is Lord Helix. Specifically, Lord Helix with Shell Armour, Shell Smash, and a Quick Claw. And a bunch of Potions, I suppose...
Unfortunately I have access to none of those things at the moment, as I'm trapped in post-Agate areas. I might just have to raise a Crustle with Sturdy and hope for the best. Bleh. I don't feel like raising a new mon for one fight. Is Crustle decent?
