Activate Phyrexian Altar by sacrificing Su-Chi Cave Guard, adding one mana of any color.
When Su-Chi Cave Guard dies, it triggers, adding eight ({C} magic symbol) .
Activate Soldevi Digger by paying ({2} magic symbol) , putting Su-Chi Cave Guard on the bottom of your library from your graveyard.
Activate Grenzo by paying ({2} magic symbol) , putting Su-Chi Cave Guard into your graveyard from the bottom of your library, and then putting it onto the battlefield.