These poor centaurs appear to have been stricken by some sort of horrible disease. Do they look a little familiar?
It's the centaurs from Coursers' Accord, also illustrated by Nils Hamm, from Return to Ravnica! That's what happens when you summon tokens into a world ravaged by anti-token plagues. On the upside, though, those centaurs probably aren't dead. They're just taking a little rest because they're not used to being only 2/2.