Apocalypse Descends: I Get Stronger by Raising Zombies

A global heat wave melts the Arctic glaciers, releasing a mysterious virus. The virus drifts into the clouds, and when a torrential downpour hits, every living thing on Blue Star is completely infected! The genes of all species mutate. The world is transformed into a blood-soaked hell! [You helped a zombie do ten minutes of squats. The zombie feels its joints have become much more flexible.] [The ten-minute jog you assigned the zombie is complete. The zombie's base speed has increased.] [You spent ten minutes explaining the ten benefits of a vegetarian diet to a zombie. The zombie has been uplifted in both body and spirit.]