Infested Thrinax enters the battlefield, it triggers, causing you to create a number of 1/1 Saproling creature tokens when a nontoken creature you control dies.
Activate
Phyrexian Altar by sacrificing
Brokkos, adding ({1} magic symbol) .
When
Brokkos dies,
Infested Thrinax triggers, creating six 1/1 Saproling creature tokens.
Activate
Phyrexian Altar four times by sacrificing four Saprolings, adding ({1} magic symbol) ({UB} magic symbol) ({G} magic symbol) ({G} magic symbol) .
Cast
Brokkos from your graveyard for its mutate cost by paying ({2} magic symbol) ({UB} magic symbol) ({G} magic symbol) ({G} magic symbol) , putting it on top of a Saproling.