I thought of this general idea for a card - do with it what you will:
Silent Menagerie
3 faeria 0/3 colorless structure (requires 1 of each color land) - creatures lose duplicate abilities when summoned.
The idea is that this could hard counter any deck that relies on repeatedly spamming a given ability or specific card. If there’s already a creature with that ability in play, the ability doesn’t trigger. So only one taunter allowed at a time, only one haste, etc. The player using this could also try to have multiple common abilities in deck, using this to limit opponents using those cards.
What do you consider as an ability? Just keywords? Which ones? Taunt, Jump, Charge, Dash, Flying I guess. But some are trickier - Combat? Aquatic (do you summon on land now?). Production? Gift? Last Words? You’ll probably want a concise definition that fits onto a card - unless you want to create a brand new keyword for it.
The idea of disabling stuff does have potential, though. Silence is a common cross-genre game mechanic and I’m guessing other card games would have it although this is the only one I know. As for limiting repeated use - another idea might be to have a creature/structure effect to damage or silence duplicate creature or structure cards at summon - IMHO it’s far simpler to do it on duplicate cards than duplicate abilities.
There’s a custom card thread here. Unfortunately they haven’t added a custom card subforum yet.
good points, it was hard coming up with adequate text. I was thinking about how adding more haste creatures to yellow could necessitate haste counters and this came to mind as a somewhat fair way to do it. I suppose a compromise on just keywords could work. The challenge with the silence concept is it needs to be done in a very careful way as if it’s too broad it’d be potentially broken, while if it’s too specific (e.g., only eliminates taunt) then it’s almost unplayable. Situational seems to be the way to go.
Also thanks for pointing me to the card thread, I’ll check it out if I come up with other ideas.