Convert to Slime gives you a three for one, and if you have Delirium, you get a fonky chonky Ooze for your troubles, making it a four for one, for five mana
You dont even need to tap it, so you can activate its abilities the turn that it comes down
His +1 is a draw, his -2 creates a creature (with flying and lifelink no less) and his -7 probably wins you the game
seem to fit the infect theme better, and with it being G/B i'd say Zombies or Insects
The Balrog, Durins Bane The Balrog was powerful enough to take down Gandalf (well, sort of) in the Lord of the Rings, so it only makes sense that the card equivalent of this creature would be extremely powerful too