The biggest problem I can see with this would be in a poison deck(fractal/mitosis + forest scorpions + adrenaline + this maybe). The creatures are small enough that they would have little to no risk of dying and the damage would add up real fast
With adrenaline Astral Bridge's effect would trigger multiple times each round, raising the percentage of dying to 20% each turn. Also this is a quite long combo, and if you don't put phase shields in your deck (Astral Bridge makes them useless) you'll probably die soon. xD
Do multiple Bridges do anything? Very interesting card; it feels like Gravity Shield though?
No, cretures "uses only a bridge/portal to attack", so the percentage doesn't raise.
True, but think of this: Aether doesn't have many powerful creatures, thus not so much chance to have creatures destroyed. I know Aether usually works well in combos, but most of the other elements, barring 
and 
, have creatures with a wide range of stats. Thus, all is balanced. Well, mostly, for I haven't much experience with Aether.
You also have to consider Aether having creatures that come onto the field Immaterial.
A card that grants all creatures on the field Momentum + The creatures not being able to die, can prove to be OP.
I know this card is has a strong connection to immortal creatures, but using this card erases your possibility of saving yourself behind a Phase Shield, and you need several turns to play immortal aether creatures.^^
Quick question, when you say it "collapses" killing the creature, is the permanent destroyed as well? I don't think this can ever exists, it would make Mono aether OP. When you run a mono aether deck the primary counters are permanent control and shields. This card gets rid of one of those counters.
No, the permanent is not destroyed, only a space fraction on the bridge/portal collapse.
In a mono aether deck you usually use 4/6 phase shields. With this card they could be useless, and maybe you wouldn't place them in your deck, and if they explode your Astral Bridge/Portal you won't have a shield nor momentum on your creatures.^^
I think I've replied to all your questions, if I've missed one post it again.
