Spiked Slime

You will never find one in the world. It arrives only as part of King Slime, and only in an expert or master world, mixed in with the plain blue ones he sheds while he bounces. The share of spiked spawns climbs as his health drops, so the closing stretch has spikes crossing the arena while you are still reading the boss. Once he dies they go with him, and the only way to see another is to summon him again.

Build wider and taller than feels necessary. The usual expert death is dodging upward off the platform into a spread of spikes fired by something you never looked at. Sweep the small ones off with anything that pierces and do not let them gather under your dodge lane.

Royal Gel does not protect you here. Slimes that belong to the fight ignore it and keep shooting and hurting you on contact, so a slot you gave up expecting a quiet arena bought you nothing. Killing them is optional: they leave nothing behind and do not count toward the slime collection achievement.

It has no bestiary entry, almost certainly because a classic player could never fill one in. Spawned into a classic world with outside tools it turns up weaker than it should be, a leftover value for a difficulty it never appears in.