As of right now you would need at least one Monolith. In order to get the Monoliths both parents have to be a Monolith (either the same or different). If you have one, you can try breeding with a friend's in the Co-Op, otherwise you would need two. I don't see this changing, but it could. You may get lucky and get one through a mystery egg though. (This applies to the Snowflake dragons as well).