Spiked Slime

The Spiked Slime is summoned by the King Slime in Expert Mode. He is summoned with Blue Slimes by the King Slime.

trivia
Spiked Slimes will, like King Slime, still attack and do damage to the player even if he/she has equipped the Royal Gel. However, the Blue Slimes that King Slime summons are still perfectly friendly. It's currently unknown if this is a bug or not.