The only real downside with them is the number of colors give access to
Living End +2 Chalice of the Void +3 Leyline of the Void -1 Lightning Bolt -1 Fatal Push -2 Terminate -1 Blood Moon Tron +1 Blood Moon +2 Pithing Needle +2 Sheoldred, the Apocalypse -1 Fatal Push -1 Lightning Bolt -2 Terminate -1 Kroxa, Titan of Deaths Hunger Rhinos +2 Chalice of the Void +2 Sheoldred, the Apocalypse +2 Engineered Explosives +1 Fatal Push +1 Kroxa, TItan of Deaths Hunger -2 Terminate -1 Lightning Bolt -1 Blood Moon -4 Orcish Bowmasters Not Dead After All creates a zero mana enchantment that will be destroyed by Engineered Explosives
This results in the perfect blend of defensive abilities, brutal Tax effects, and consistent combos thanks to the plethora of Tutors in the deck
A lot of this Merlin cards usefulness seems dependent on whether it can take advantage of cards like Mickey Mouse Wayward Sorcerer or Dr
Once its played, and as long as it remains on the battlefield, it gives each of your Zombies a +1/+1 buff
This means that if your commander gets destroyed and you let it go to the graveyard (or any another zone), you wont have to pay the tax if you end up casting it from there