The idea is awesome and the art is good and really fitting!
I only think that the card should explain that the creature will try to free itself and how many HP would the chains have (i feel that Enchain should have more HP, at least to hold a dragon for 2 turns).
What if i cast a reverse time on a chained creature?
What if i freeze them?
How the chain are represented? With counters like poison that shows how many HP the chains have?
It's really interesting, but i'd like to have more info!
Also, congratulations for being promoted to the Forge!
I think it's just a "10 damage block". Example, i put this on a 6 att creature:
turn 0: chains have 10 HP.
turn 1: chains have 4 HP
turn 2: chains die cuz of the attak.
Notice any other effects are aplied, as: Adrenaline caounts as multiple attaks, so if i have a 1 HP chain on a 3 att creature and i put adrenaline on it, the chains will block the 1st of the 4 attaks.
If the creature is frost, it doesn't attak (chains are not damaged).
A blocked creature by a warden or turtle shield is the same as frost.
etc.
So making a little analysis...
BB blocks for 6 turns, unblockable.
Enchain only blocks for 5 turns a 2 att creature, 4 turns a 3/4 att creature.
As it's soft CC (it can be broken by any damaging spell or skill), make it be a 20/30 damage block. That way, it blocks creatures "more than BB" but they can be broken. Dude, i have just gave you a pros/cons analysis xD
