You control a creature that can tap to produce at least ({G} magic symbol) .
Steps
Activate the mana-producing creature by tapping it, adding at least ({G} magic symbol) .
Activate Phelddagrif's first ability by paying ({G} magic symbol) , causing Phelddagrif to gain trample until end of turn and causing target opponent to create a 11 Hippo creature token.
The Hippo enters the battlefield, triggering Intruder Alarm and Suture Priest's second ability.
Resolve the Intruder Alarm trigger, untapping all creatures.
Resolve the Suture Priest trigger, causing the Hippo token's controller to lose 1 life.