Keyword Challenge

{kefke}
I don't have anything to say against the ability itself but as a keyworded mechanic I think it's too narrow. Crewing a vehicle is usually not something that happens often enough to justify a keyword. I'm in general not much of a fan of mechanics that piggyback explicitly on other mechanics because it is not only narrow but it also takes away the focus of both mechanics.
Furthermore, I'm not even sure the rules support your keyword because you have to tap creatures with a certain total power to crew a vehicle. So the vehicle isn't crewed before the power(s) are checked, making your mechanic trigger only when it is too late.
As I said, I get the idea and like it somewhat as a one or two of ability, but as a keyword, I don't see it.

{maiapologies}
Negative keywords are bad design. Negative keywords that have the potential to cripple your game plan severely are even worse. I don't mind your card on it's own but keywording something negative for the caster is a big no-no. As an idea, you could try to turn around the mechanic to make it positive while still maintaining the flavor.

{Tesagk}
It's Once upon a Time in mechanic form! I like the idea of Once upon a Time and I also like your mechanic. It generates the same interesting tension where you want to have as many of these potentially powerful spells in your deck but at the same time you don't want to play them in multiples because it makes them worse. The only issue I have is that in singleton formats like commander, your cards will almost always be primed which takes away a lot of what makes the mechanic cool.

{sdfkjgh}
Well that's quite a weird mechanic. It appears to be a silver bordered mechanic although it actually works well within the regular rules' framework. I very much enjoy the word play and the wonkyness but am also a bit worried that it will result in too much counting and feel bad situations when the opponent just destroys one of your permanents at the right time.

{viriss}
Looks a lot like exalted but actually would play somewhat different. You would probably try to use different attackers every time to buff your army evenly. I like it for its simplicity and flavor even though it might be a bit too close to exalted.

{kilenc}
I like your mechanic far more than your cards. That being said, I like your mechanic actually quite well. A reverse exert seems like a cool idea and is also flavorful. There are some issues I have with your execution, though: 1. Wording. You could just make the ability “<cost>, : Prime CARDNAME until it untaps.” and “Whenever CARDNAMES untaps primed, [effect].” This way you could create more diverse effects without being wordy and you would allow for players to “break” the mechanic by untapping the creatures in the same turn they primed them. Similarly to “breaking” exert by giving the creature vigilance. 2. Inherent in your mechanic is a long setup time. You cast the creature, then wait a turn. Then you prime it and have to wait another turn. Unless the creature has haste, it will take two full turns to do what it is supposed to do. Two turns where the opponent has time to prepare and/or remove your creature. So these effects have to really be worth it! A simple +2/+2 and trample will likely not be enough to make people get exited about your cards. Your mechanic is a full hearted timmy mechanic and the cards should reflect that.
All in all, I think you had a pretty interesting idea and therefore I would like to ask you whether I can add a modified version of your mechanic to my mechanic collection. It's usually just my private compilation of keywords from the forums that I use for myself but sometimes I offer others to help find a fitting mechanic for their sets. If you don't mind me using your mechanic's idea, I would (given the right circumstances) recommend it to other designers while still giving you credit of course.</cost>

{And the winner is...}
Kilenc! With Viriss basically head to head. Although I liked Viriss' execution far better, Kilenc had the bolder idea and I want to see more of him/her.
Thanks everyone for participating!