While I can't wait to someday get a flip planeswalker of him in similar fashion to Nicol Bolas, the RavagerNicol Bolas, the Ravager, I still think that for now we should do the non-obvious thing and allow the most legendary Spirit Dragon to compete, despite technically not being a Dragon or a Spirit
Keep an eye on Elder Gargaroth, though once Teferi, Time Raveler rotates out of Standard in the fall, it may have potential
Or maybe your decks designed to draw your entire library and use this as a finisher
Normally, I'd now examine the effect and history of the spiking card, but in this case it doesn't seem like anyone is purchasing it based on the rules text
Im looking forward to seeing some of the flagship D&D monsters which WotC wouldnt normally allow into Magic settings finally get their cardboard incarnations