Three Diamond Fusion.

She doesn’t actually stand straight up like in those two pics on the right. Just drew those so you can see her outfit and colors. Mostly she’s crouched and/or crawling.

She’s humongous and doesn’t come into existence often as there’s no reason for the Diamonds to fuse and she’s just overkill in any situation…. unless you need a planet purged or something.

Steven would be around the size of her pupils.