Once hes summoned, you get to amass a five-strong Orc army, and mill five cards to the graveyard, then choose one creature card from that lot to play immediately on the battlefield, with no need to pay the Land cost
If I recall correctly, this began in the core set with Garruk, Primal Hunter with a rough five-cost with triple Green, but then +1 to make a 3/3 Beast that's Green or -3 once to draw
Payout is 70% of the total entry fees to Top Cut in typical deviation
The strange thing about Hyalopterous Lemure is its artwork, as it depicts a fluffy monkey with butterfly wings, which hardly fits with the aesthetic of black cards
Hexproof addressed that issue but created its own: piling a bunch of improvements onto the same creature that an opponent can't interact with