The Great Santini's Marionette

(Activate only if 3 of 3 parts are on the battlefield. Activate using Showmans Resonance.)
When The Great Santini's Marionette enters the battlefield, count up X, being the number of mana spent to cast. Gain control of that many of your opponents creatures with power 4 or less. Untap lands if mana is left over.
Sacrifice X controlled opponents creatures, untap all lands. Gain 1 life per sacrificed creature. Activate only as a sorcery.
"These strings, you cannot break."