Does this work or not: You make the call!

Active Player: “Acidic Slime?”
Non-Active Player: “Sure. After it resolves, I cast Cloudshift on my Zealous Conscripts. I take your slime and use the trigger to destroy your Ring of Kalonia!”

Spells and abilities begin their time on the stack controlled by the player who puts them there, and triggered abilties are put onto the stack by the player who controls their source when they trigger. There are a number of spells and abilities (such as Redirect or Spellskite) that allow you to change spells on the stack by selecting new targers, but very few indeed change their controller. Those that do so are all explicit in the fact they say you gain control of it, because they MUST be.

Just as removing the source of an effect does not remove the effect, changing the control of the source of a triggered ability does not change control of the ability on the stack.

As you know by now, Acidic Slime has an ability that triggers when it enters the battlefield. When it does, it is normally controlled by its caster. It is at this point that the game checks for triggers, the ability is put on the stack, and the controller of the ability is set. It doesn’t matter at this point if someone kills or steals (or even simply borrows) the Acidic Slime; the ability will do what its controller selected.

If you said it doesn’t work the way the Non-Active player wanted, then you made the right call!

Today’s Rules Tip written by
David Hibbs, Level 3 judge from League City, TX