The Kamen Riders have a few things in common, and not all of those are material. For one thing, so far most of the riders were lured into the game with a promise that if they survive all the others (preferably by killing them), they will get their heart's desire. Unfortunately what none of them know is that the game is surely rigged.

The cards are called Advent Cards and they all look like this on the back:

The first card in the deck is Seal. It blocks the monsters more effectively than any wall. In fact some of them turn and run upon sight of it because the more intelligent ones know that if someone has the seal card, they probably have... a Contract card. There's some question about it, but the Contract card is not optional for the monster. Once exposed, it is bound to the bearer until that person loses his or her deck. Mind, neither Contract nor Seal card denotes safety from the monster, even after it is bound to you. Kamen Rider Scissors, when his deck shattered, was immediately munched up by his. Ryuuki almost committed suicide by his. Oja's trio are very demanding on him, but his spirit is wild enough to contain them.

Who's used this card, anyway? Some of the cards are not marked for specific Riders, and may be in each of the decks, such as Return, Copy, Steal, Confine and Unite. Cards that ARE marked for specific Riders will only output to them, no matter whose visor they are input to.

Both Raia and Verde have Copy Vents. I couldn't say about the others, as yet.

Once you've become a Rider, you get a ride. Specifically something called a Ride Shooter, which takes you speedily into the Mirror World, but seems to have no other real use. One you've found your monster, you get out and fight.