#control-changing effects

[magicjudge]

Theft question: If I use a theft spell like "Threaten" or "Price of Loyalty" that let me have control of a creature until the end of the turn. Then I cast Slip Out the Back. Since this phases out until my next turn, and I am still the controller when the end-of-turn effect hits, do I keep this creature permanently?

Threaten's effect will still wear off while the creature is phased out, so it will phase in under its previous owner's control. Phasing a creature out doesn't stop these sorts of effects from wearing off. Not even "end the turn" effects can stop them.

What's unexpected is that the creature won't phase back in on its previous controller's next untap step, but rather will phase in on your next untap step instead since you controlled it when it phased out, so at the very least this will delay the creature's return a bit.

[magicjudge]

This happened to me and enough people disagreed with me I let it happen, since I didn't understand the ability well enough to know, myself. If a opponent casts Act of Treason on my Kotose, the Silent Spider, can they then cast the card I previously exiled with her triggered ability?

Good news: Your opponent cannot cast an exiled card. The entire effect is part of her ETB triggered ability, so changing control of Kotose doesn't suddenly allow someone else the ability to cast it. (It would need to be a separate ability on Kotose for that.)

Bad news: You can't cast the card either anymore, since you've now lost control of Kotose and even when you get her back in the cleanup step, the duration for her last clause has lapsed and can't be restored for any card she has already exiled.

[magicjudge]

If someone casts Treachery on my Elesh Norn, Mother of Machines, do they untap 0 lands or 10?

You'll get two triggers to untap five lands.

Control of Elesh Norn will change as soon as Treachery is on the battlefield, and as such you'll control her when Treachery's ability would trigger and as such it will trigger twice.

[magicjudge]

Hello! We are in a game of commander. A creature has vapor snare attached to it. Someone goes to take control of this creature with memnarch’s activated abilities. How does this resolve? Does the enchantment stay attached and return to the vapor snare owner or does the enchantment lose relevance? Thanks in advance!

Vapor Snare will remain attached to the creature, but Memnarch's controller will control it.These two competing control-changing effects are both still applying to the creature, but the Memnarch player actually controls it because that player's effect is most recent.You still control Vapor Snare, however, and will still have to pay its upkeep cost or sacrifice the aura.

[magicjudge]

If I use a card like Control Magic, to steal a creature that was cast with suspend, can it attack/activate tap abilities? TLDR does it still have haste?

No.

The rules for suspend specify that the haste granted to the creature only lasts until you lose control of the spell or the permanent it becomes.

[magicjudge]

Rules question: Exert. How long does it stay on the creature if I am not the controller of it? Example: I steal an Exert creature and attack with it. It's now exerted by me and when it returns to my opponent it does untap because it was not exerted by him. Then in his turn he make it tapped. But in his turn I use a permanent control effect. Now my turn again, there is the tricky part: will it untap or is it still exerted by me? And what if I steal it a few turns later?

It won’t untap.

It’s your next untap step after you exerted the permanent, you control it, and it would normally untap, so exert’s effect applies and keeps it from untapping here. It doesn’t matter that it has untapped normally under another player’s control since it was exerted.

[magicjudge]

If I cast Frenzied Fugue on my opponent's creature, then destroy fugue during my turn while I have control of the creature, does my opponent still get the creature back at end of turn since the source of that trigger is no longer on the battlefield?

The creature still goes back to its owner in the cleanup step.

Frenzied Fugue’s triggered ability sets up a control-change effect with a limited duration, and once that duration ends, the control-change effect also ends. It doesn’t matter if the source of the trigger is still on the battlefield at that time.