If it is UP, perhaps change mechanic to enter burrowed? Then unburrow for . Of course the name could be changed.
First thought: What?!Second thought: Actually very neat idea rainbow has dragon! I like it!Third thought: I don't like the name. What about Rainbow Dragon or Elemental Dragon? To highlight that you need all elements to use it?BTW I think we need more Other cards so big thumb up from me for this idea
Hmmm... the wording is very awkward but I like the overall idea.It seems a little UP to me though. It effectively costs 15 + 12 for a 10|10 ... granted supernovas would make this quite doable, but it does seem very expensive nonetheless.
I recommend removing 'The' from the card name, and just leaving it as 'Forgotten Dragon', to match the other dragons in-game.