Well. Blue certainly has lots of tempo-controlling cards. Where other colours are happy to get rid of threats, blue is happiest just... postponing them a while.
Hmm. How about that for an idea. An artifact that lets you lock away a threat for a little while. Maybe a single slot prison, and you have to let the old inmate out to put a new one in.
Powerful - because that's an o-ring on their best creature at all times. But they get a benefit when you move it. And I think I can set this up like the old "We have two ways of equipping this" to do it sneakily and give blue the benefit; while letting you use it as an entire alternative way of slowly flickering your own stuff.
So here we go; with slight mangling. A nasty threat to leave open for blue; but perhaps usable by others too.
Costs... Well, this is kinda sorta Tawnos's Coffin? So sure, 4/3 is probably right for the offensive use. We can keep the 'your creature' use cheap, I think.
Annnd... eww. This ended up WAY wordier than I wanted. Ok, removing equip reminder text (that's evergreen enough now, right? though I'll miss the 'as a sorcery' part...) Lose the final "to a new creature" and turn 'a' to 'next'... Ok, that'll do.
Did I hit the brief? Well, it's an artifact; and it uses blue. Check there.
Not too wordy for an uncommon; though certainly not common. Did I overpower it to rare though? Maybe? It's 7-mana removal. That's not particularly powerful for most. And the idea of serially flickering all your creatures on your own turn is certainly a build-around kind of hint for something. So ok, rarity is OK I think.
Is a tempo deck really going to be wiling to miss its 4-drop (or, more likely, its chance to mess up the opponents 4-drop) in exchange for having this around? Probably; actually, since it can snag their 4-drop on their turn 5 if they don't drop a more immediate threat.
So yup, I think this'll do. Neat. (oops. Forgot to roll the cmc. Hope I rolled a 4!)
I think this is a bit better than you're giving it credit for. It effectively keeps two creatures out of combat if you pay per turn, and that scales up to 3 if you pay 6 mana per turn etc. The first removal of 4+3 seems fine, but the 3 at instant speed to switch what's imprisoned seems a bit too good.
And I fear the use of this to flicker your own creatures might be a bit too cheap too. It goes instantly infinite with Priest of Gix/Priest of Urabrask/Ardent Electromancer with party of 3+, and gives you infinite ETB reuses with Burning-Tree Emissary. Never mind that in a typical ETB/flicker deck I'm very happy to play Cloudshift or Momentary Blink; this is more at the power level of Deadeye Navigator, which... I think was banned in EDH? Many people consider it way too good, anyway. A card that's the same rate to flicker one creature, twice as cheap to flicker two creatures, and can be used on opponents' stuff too? Yeeaah, I fear that's a bit cheap.
See Challenge # 167. Rolled Blue Uncommon Artifact; tempo.
Well. Blue certainly has lots of tempo-controlling cards. Where other colours are happy to get rid of threats, blue is happiest just... postponing them a while.
Hmm. How about that for an idea. An artifact that lets you lock away a threat for a little while. Maybe a single slot prison, and you have to let the old inmate out to put a new one in.
Powerful - because that's an o-ring on their best creature at all times. But they get a benefit when you move it. And I think I can set this up like the old "We have two ways of equipping this" to do it sneakily and give blue the benefit; while letting you use it as an entire alternative way of slowly flickering your own stuff.
So here we go; with slight mangling. A nasty threat to leave open for blue; but perhaps usable by others too.
Costs... Well, this is kinda sorta Tawnos's Coffin? So sure, 4/3 is probably right for the offensive use. We can keep the 'your creature' use cheap, I think.
Annnd... eww. This ended up WAY wordier than I wanted. Ok, removing equip reminder text (that's evergreen enough now, right? though I'll miss the 'as a sorcery' part...) Lose the final "to a new creature" and turn 'a' to 'next'... Ok, that'll do.
Did I hit the brief? Well, it's an artifact; and it uses blue. Check there.
Not too wordy for an uncommon; though certainly not common. Did I overpower it to rare though? Maybe? It's 7-mana removal. That's not particularly powerful for most. And the idea of serially flickering all your creatures on your own turn is certainly a build-around kind of hint for something. So ok, rarity is OK I think.
Is a tempo deck really going to be wiling to miss its 4-drop (or, more likely, its chance to mess up the opponents 4-drop) in exchange for having this around? Probably; actually, since it can snag their 4-drop on their turn 5 if they don't drop a more immediate threat.
So yup, I think this'll do. Neat. (oops. Forgot to roll the cmc. Hope I rolled a 4!)
I think this is a bit better than you're giving it credit for. It effectively keeps two creatures out of combat if you pay
per turn, and that scales up to 3 if you pay 6 mana per turn etc. The first removal of 4+3 seems fine, but the 3 at instant speed to switch what's imprisoned seems a bit too good.
And I fear the use of this to flicker your own creatures might be a bit too cheap too. It goes instantly infinite with Priest of Gix/Priest of Urabrask/Ardent Electromancer with party of 3+, and gives you infinite ETB reuses with Burning-Tree Emissary. Never mind that in a typical ETB/flicker deck I'm very happy to play Cloudshift or Momentary Blink; this is more at the power level of Deadeye Navigator, which... I think was banned in EDH? Many people consider it way too good, anyway. A card that's the same rate to flicker one creature, twice as cheap to flicker two creatures, and can be used on opponents' stuff too? Yeeaah, I fear that's a bit cheap.