Whenever an opponent draws a card, that player loses 1 life
There is no specific limit to how many planeswalkers are allowed on a deck
Follow up with the reanimation aura to blink your board and put Worldgorger back in the yard again
It looks at creature types that do have Commanders, but the options are lackluster

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The best target, however, will almost always be Merlin, Goat, who truly seems to be the G.O.A.T