Twilight Drover has at least one +1/+1 counter on it.
({1} magic symbol) ({W} magic symbol) available.
Steps
Activate Twilight Drover by paying ({1} magic symbol) ({W} magic symbol) and removing a +1/+1 counter from it, creating two 1/1 Spirit creature tokens.
Activate Phyrexian Altar twice by sacrificing the Spirits, adding ({1} magic symbol) ({W} magic symbol) .
When the Spirits die, Twilight Drover triggers twice, putting two +1/+1 counters on itself.