Previous Versions can be seen here.

Contamination is a Perseverance deck specific effect card.

When used, it kills all monsters that are under KR and will add a random Perseverance spell (except another Contamination) to your hand with -1 cost for each kill it does.

It's best used alongside cards that do small damage to many things like Woshua and Pollutant Gas, but can also be good alongside Poison, which you can use to give KR to any monster you want and, if it's later in the game, keep repeating it so you can wipe the board and gain many spells.

It is very costly though, not to mention it will fill up your hand, so it is usually reserved for the late-game when you have money to spare.