MArcomage

Just an idea I came up with: Negating the effect of some (non-token based) keyword with another. Most obvious example that comes to mind is Restoration and Destruction. For instance;
Player 1 plays Uncommon Destruction card
Player 2 plays a Restoration card (of X rarity)
Player 1 can no longer trigger the Destruction keyword this turn. He could, of course, play another Destruction card and try again next turn.

It would work the same in reverse, so Destruction also counters Restoration. Other keywords such as Illusion, Nature, Horde etc. are a bit less obvious and need more thinking to set up.
Or it could also be a whole new keyword that interrupts some keyword effects (or a reworked, existing one).

Thoughts welcomed.

I believe it would be fairly hard to set up for admin

Also there's only 4 ketwords - destruction, illusion, aqua and restoration which work in chains

Without some kind of visual way to show that the effect is being blocked for said turn, I think implementing something like this would cause a lot of confusion and "bug" reports from people who don't understand why something didn't trigger.

For the difficulty of setting it up, I have to disagree. To me it sounds simple enough to have one extra line of code for these keywords that checks opponent's previous card.

However, I have to agree with DPsycho here; it would most likely create a lot of confusion unless its effects are made very clear. It may also be more complicated than necessary. Hard to say without seeing it; potentially really fun, potentially confusing and annoying.