It gets a blocker or other annoying creature out of the picture and grants a potentially sizeable buff to Commander Damage
Infernoid Evil can also search out any Void Spell or Trap if it's sent to the Graveyard or banished, which will happen when Instant Fusion destroys it anyway
I guess you can drop it on different players each time day and night flip, which might be a suspenseful good time if your group's threshold for fun is really low
Negate all Continuous Spell Cards during the turn this card is activated.
The likes of Waste Not, Harmonic Prodigy and Jeskas Will can help you get Kefka flipped quicker, by adding mana and doubling up on hand attack
As always, remember that desirability, rarity, and time are the keys to success when investing in Pokmon cards