Worldslayer doesnt have any built-in outs to end the game, and instead resets the board completely
Triskaidekaphile is probably worth a slot since putting lands into your hand at instant speed could creep you up to thirteen cards and the win condition, and other than that, the card draw ability and no maximum hand size are going to be useful
Sygg, River Cutthroat Sygg, River Cutthroat is a very cheap commander, making it easy to keep on the board
I also haven't done this for any other deck, but if you're willing to dish out a few extra bucks I highly recommend picking up Calamity of the Titans, Desecrate Reality, and Not of This World, they're all under $5 each but they are incredible for the deck
1 Marrow-Gnawer Fear The Rats Marrow-Gnawer is the primary commander for Rat decks if you're building one, and even if you aren't using it as a commander, it's the best Rat card there is