All permanents on the battlefield (Battle of Hoover Dam with "Legion" chosen).
You control at least one additional creature.
Steps
Activate Ashnod's Altar by sacrificing another creature you control, adding ({C} magic symbol) ({C} magic symbol) .
When the creature dies, Battle of Hoover Dam triggers, putting two +1/+1 counters on Ghave.
Activate Ghave's first ability by paying ({1} magic symbol) and removing a +1/+1 counter from it, creating a 1/1 Saproling creature token.
Repeat.
Notes
Once you have infinite +1/+1 counters on Ghave, you may target any other creature with Battle of Hoover Dam's trigger instead. You may also forego sacrificing the Saprolings.