One of the characters is an otter.

You play as an otter.

You play as otters.

You can tame otters and they have multiple uses, like pets or fishing partners.

You can't have an otter as patronus, in fact, you can't have a patronus at all. 0/10

Megalenhydris can be added via mods. River otters can be added too, but have weird biomes and temperature restrictions that need manual editing. It's possible to mount them into battle with mods.

Inclues giant otters and small clawed otters as DLC.

May include otters

Very cute game that might include otters.

Another great fighting game that uses Otter UI.