Phorkey, ShapeShifter, and Frank

 are loyal subjects of King Neptune and Queen Amphitrite. They appear in SpongeGod and Triton as supporting characters, where they failed to help everyone escape and ended up joining them in their fate.

Phorkey
Phorkey is a wise purple hag with the power of controlling ice. He is grumpy and looks kind of like Squidward. He wears a red robe and has messy gray hair and beard. When he tried to make an icy path to slip Iko's guards, he only ended up slipping Mr. Krabs and Squidward. Phorkey is kind and gives good advice.

ShapeShifter
ShapeShifter is a mutant green creature that can change an object into a different shape, thus giving the name. He is very hideous to mortal girls who scream at one look of him. He sings so beautifully, he makes glass break. When he tried to make a building fall on top of Iko, Iko used his tail to hit the building, causing it to fall in the opposite direction on top of Patrick and Sandy. ShapeShifter likes to prove himself as a leader and thinks he's the smartest one in the group of royal subjects.

Frank
Frank is a mud monster made of, well, mud. He can turn himself into liquid and squeeze into the tiniest cracks. He can shoot mud balls at an unsuspecting victim. He looks kind of like Patrick. When Frank tried to stop Iko, Iko squashed him before he could throw something at him. Luckily, Frank was unharmed. He's quiet most of the time, and although he looks ugly on the outside, this monster has a good heart.

Non-fanmade:
The Clash of Triton

Fanmade:

 * SpongeGod and Triton