Twilight Drover has at least one +1/+1 counter on it.
({2} magic symbol) ({W} magic symbol) available.
Steps
Activate Twilight Drover by paying ({2} magic symbol) ({W} magic symbol) and removing a +1/+1 counter from it, creating two 1/1 Spirit creature tokens.
Activate Phyrexian Altar by sacrificing a Spirit token, adding ({W} magic symbol) .
When the Spirit dies, Twilight Drover triggers, putting a +1/+1 counter on Twilight Drover.
Activate Ashnod's Altar by sacrificing a Spirit token, adding ({C} magic symbol) ({C} magic symbol) .
When the Spirit dies, Twilight Drover triggers, putting a +1/+1 counter on Twilight Drover.