Its an impressive power boost but, at only five mana, youd best believe theres a drawback
You can find other recent Commander set reviews here: This time around, were doing things a little differently
First you need the enemy knight Lezales to spawn with the Pisces sign (so he has worst compatibility with Gafgarion), Item for his secondary skillset, and the ability to use Potions unlocked, and then you need to be able to kill everyone else but Gafgarion and Lezales (which itself requires a ton of luck to do before Lezales dies, especially with killing Agrias)
Armageddon From casual to competitive, almost everyone knows Armageddon
Are we talking about less than 1,000 cards
Plus, keeping one mana up as a Blue player is a completely natural thing to do, and just the threat of this card will have your opponents reconsidering their life choices