Compared to Zedruu the Greathearted, Blim is a lot more difficult to build, mostly for the fact that he’s a 4/3 flyer. In order to maximize him, I’d go with something like Assault Suit and a swampwalk enabler with Urborg, Tomb of Yawgmoth, just for the pure chaos, and to maximize his ability. Plus he becomes less of a ‘threat’ and more of a ‘weapon’ that way.
For card ideas, there’s not a ton off the top of my head that I can think of, but any Lich type effect works good for an early-ish kill. Demonic Pact is another lose the game you can give somebody. Demonic Lore nukes card draw decks. Demonic Taskmaster works well too, or Akroan Horse if you want more of a group hug theme.
Some curses are controlled by the cursed player, again making Blim slightly more viable. A few other cards that work well that come into play under opponents control are Pendant of Prosperity, Sleeper Agent and Xantcha (basically the same idea, Coveted Jewel which is counterintuitive so opponents don’t attack you, but besides that there isn’t a lot you could use. And, aura enchantments you put on opponents creatures you still control, which really sucks for making Blim a fantastic commander.
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