Activate Grim Monolith's first ability by tapping it, adding ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) .
Activate The Blackstaff of Waterdeep by paying ({1} magic symbol) ({U} magic symbol) and tapping it, causing Grim Monolith to become an artifact creature until end of turn.
Activate Grim Monolith's second ability by paying ({2} magic symbol) , untapping it.
Activate Grim Monolith's first ability by tapping it, adding ({C} magic symbol) ({C} magic symbol) ({C} magic symbol) .