This creature doesnt untap during your untap step
The Phyrexians are making Mite tokens, which are all 1/1s with Toxic 1 that cant block, and the other side is making 2/2 Rebel tokens that come in attached to equipment with the For Mirrodin
Best Rummager Payoffs Anything that lets you see more cards in red is good, so already this is an okay payoff
He comes in with haste, menace, and MTG ward 2 for protection, and when he attacks, you get to sacrifice your whole board and then play a bunch of instant and sorcery spells off the top of your library for free
I can put this another way: aggro player, would you pay five mana for all your creatures to be unblockable for a turn, with the upside of some of your opponent's creatures also destroying each other