As mentioned on Debt of Loyalty, I'd like some non-red non-blue control change effects. Black has precedent in Enslave, but slavery isn't a concept that's particularly prominent in the series (and Enslave is also from Planar Chaos), so this is a top-down design based on the concept of blackmailing an enemy to your side, as Lelouch does with Villetta (who he already used his Geass on much earlier).

It's probably a lot easier to trigger than Debt of Loyalty. Cost is a guess, but might need to be a bit higher. (Though for 5 mana you can just get flat-out Mind Control...)

A couple of possible art crops from the key scene, neither of which is ideal.

­ or .

Jenesis points out that this will most easily and most simply gain control of creatures that are tapped. I'm considering making it only target untapped creatures.

Or "Gain control of target creature that could have blocked this turn but didn't"? I guess it depends if you want this to combo with your "don't block" effects or not -- either way the flavour is quite good.

I also slightly wish "enchant x" was only checked when you first cast an aura so cards like this could be "enchant target tapped creature. you control enchanted creature" or whatever and not fall off. It seems auras "falling off" due to things changing quite rarely matters.

There's always the Dream Leash template... though wow, that's got rather ugly with errata. "You can't choose an untapped permanent as Dream Leash's target as you cast Dream Leash"? Eww.

I really like this effect and the flavor behind it. What about this? "Choose target untapped creature that didn't block this turn. If you attacked this turn and its controller was the defending player, gain control of that creature.".
... Never mind, your wording is probably better.

You could use "target untaped creature" and remove the "and that creature did not block" if you wanted. It would be rather Black to accuse someone of complicity merely for being alive after combat... falsely accusing the Ardent Militia of working with the enemy merely because they did not sacrifice themselves...

This got used in playtesting. It is indeed obviously pretty easy to trigger. It didn't feel backbreaking when it was used, so it might not be overpowered (though it could easily go up to 5 mana if need be). Amusingly in fact I think it was used on a creature that had already been stolen with a ­Propaganda Officer or a ­Geass of Desertion.