Its fairly solid by all accounts, with its intimidating porcupine/dragon design, decent stats, and potentially powerful effect (when a Monster the player controls is destroyed by a card effect or by battle, Interplanetarypurplythorny Dragon can be Special Summoned from the hand)
If your commander is something like Emry, Lurker of the Loch, you can pitch your hand to Lions Eye Diamond, take the three blue mana to cast Emry, and then on a later turn use her to recover the Lions Eye Diamond plus any other artifacts you pitched
Plus, with the control you already have, it's overkill
Use its high HP to soak up hits while using disruption supporters like Bosss Orders to trap a non-attacking Pokmon in the active spot, forcing the opponent to run out of cards
9 loyalty Player 3 - During his or her upkeep, Player 1 uses Teferi, Master of Time to use its first ability to +1 and Loot
It offers you a bit of defense by stunning an opposing creature when you get attacked, and with proliferate, its not untapping any time soon