I'm personally for an `au:` prefix, like the `meme:` prefix. We need more quantifiers to make sense of all the possible tags now, especially obscure ones.
[@Background Pony \#7C7A](/forums/tagging/topics/general-tag-discussion?post_id=5239086#post_5239086)
Seamless seems like a good choice for that. `repeating` has also been used once.
Also, a quick google search shows that 'unicorn deer' are a thing, so I'd just go with that. A [Shadhavar](https://en.wikipedia.org/wiki/Shadhavar) is visually similar based on that wiki image, but doesn't have the same horn properties.