We're designing custom cards to put in the Horde Deck and the Survivors' Cube. However, there are already lots of Magic cards out there. Like 13,000ish at time of writing. If there's something that could be printed on an ordinary card, we'd like to avoid making a custom one for that and just obtain a regular card from our Friendly Local Gaming Store. We're trying to have a fun limited environment, but designing a full 400 card cube from scratch is a lot of work. And there's no shortage of perfectly good cards to use, no need to reinvent any Magic wheels. But there is design space that doesn't exist in ordinary Magic and is unique to Horde. I'll talk about just one particular piece of design space, the Horde's reveal action.
The Horde reveals cards from the top of its deck until it reveals a non-token card, then plays everything. This is something that doesn't occur in ordinary Magic. That means there is some design space we can fill up without making anything that is similar to an already printed Magic card. We used this to design the one mechanic unique to our Survivors' Cube, which we are calling "Clutch".
"Clutch" got its name because these cards give you a bonus when you really need it: when the Horde reveals a bunch of tokens. Each card with Clutch has a number, and when the Horde reveals that many or more creature tokens, it triggers. Because of the way we've decided to have the Stack work for the Horde's reveal, a few effects we would have liked to have don't work, since the tokens aren't yet on the battlefield when Clutch triggers. This is a somewhat unreliable mechanic (since you have only a little control over how many creatures the Horde reveals). Creatures with Clutch abilities tend to be stronger the higher the number (thus, strength is inversely proportional to probability of triggering). Clutch goes on permanents. Though currently it is only on creatures (and one artifact), we could put it on an enchantment or land.
It's an italicized mechanic like Morbid or Battalion from recent releases, but the triggering number varies from card to card. I'm not actually sure if this is OK with the rules of the game. Since the text varies from card to card, it's certainly an ability word, not a keyword. But other ability words like Threshold and Battalion are always "seven or more cards in your graveyard" or "attacking with three or more creatures". So this may be bad design. If it were changed to "always 4 creatures" or something, we'd lose a couple designs and have to rebalance but it wouldn't kill the mechanic. If someone rules-savvy knows the answer to this, please drop me a line, contact info is in the About tab.
We had a few choices when setting up this mechanic. One option was a "Horde Storm" type mechanic, that copied an effect once for each token the Horde revealed. Given how broken Storm already is, we decided not to do that. The other option we passed on was "When the Horde reveals exactly <clutch> tokens, do <effect>" While this elegantly captured the "when the horde reveals zero" effect, it made the other effects much less likely to trigger. I ran the statistics and graphed them. X or more also won't lead to the feels-bad moment if the Horde revealed just one too many tokens.
So that's the first iteration of our Clutch mechanic, which we are starting playtesting. More Clutch cards can be seen in the Custom Cards tab.