No, participant C will maintain controlling it.
Each spells have steady results which modify the creature’s traits in Layer 2, and the one with the newest timestamp wins. It would not matter that Act of Treason is barely non permanent (and one might say Donate would not have a length in any respect):
611.2a A steady impact generated by the decision of a spell or potential lasts so long as said by the spell or potential creating it (equivalent to “till finish of flip”). If no length is said, it lasts till the tip of the sport.
Related components of the layer system:
613.1b Layer 2: Management-changing results are utilized.
613.3. Inside layers 2–6, apply results from characteristic-defining skills first (see rule 604.3), then all different results in timestamp order (see rule 613.7). Notice that dependency might alter the order through which results are utilized inside a layer. (See rule 613.8.)
The scenario would have been totally different if Act of Treason had learn one thing like
Achieve management of goal creature. On the finish of flip, return it to it is proprietor’s management.
as a result of then that final half can be ‘later’ than, and overriding the impact of, your Donate.
A associated instance: you solid Donate on one in every of your creatures and provides it to Participant C. Participant A casts Act of Treason so it comes underneath Participant A’s management; on the finish of flip, it is returned to Participant C, to not you.
