Unknown
Unknown are entities from before and/or beyond Ouroboros itself. They are regarded as pure fiction; the concept of a "before" or "beyond" the boundless, all-compassing Ouroboros, source and end of all things in perpetuity... Well, that'd be difficult to believe, wouldn't it?
Perhaps... Ouroboros is neither infinite, nor the only one of its kind...?
...And, perhaps, the Unknown can be very skilled mimics...?
(Most Unknown perished in the eventuation of Ouroboros, a being destined to become everything and nothing. In the time before time, they occupied a universe known as the First Verse.)