This thread is awesome.

Really love some of the ideas, not because they are all simply useful but because they capture the flavour of AST.

Ok so I will have a go.

Seventh Gate: Wild (Diurnal)
Seventh Gate: Abyss (Nocturnal)

Naturally ability changes style for each sect, but does the same thing.

Recast: 60s (during this recast time no cards can be added to the Seventh Gate.)
Each time you Cast or Royal Road a card a portion of its power is sealed within the Seventh Gate. (Only works in Combat)
Activate Seventh Gate to unleash all card effects upon a single target for half their original duration. These card effects overwrite all other cards and cannot be overwritten by any other card. Effected by Royal Road. (so can be expanded, extended etc)
So in Diurnal if it stored Spear and Balance, your target would get Wild Spear and Wild Balance. In Nocturnal they would get Abyss Spear and Abyss Balance.

Additional Effect: If all six card effects are stored within the Seventh Gate all cards unleashed by Seventh Gate are effected by Expanded, Extended and Enhanced Royal Road at the same time.

Basically another way to manipulate your buffs and the only way to stack card effects with each other.

I also envision the casting animations change depending on Sect to fit the mood of each ability.

Would it be overpowered as hell? Yes! fun though !