Cursed

To collect the Cursed achievement, collect 100 of the Cursed Hazel Pigrum card, which is a Platinum Card.

Strats
100 Hazels seems like a lot at the beginning of the game, because it is a rare platinum card. However, once you have entered the Shadow Realm, Cursed Hazel Pigrum is a very common card in Shadow Packs.

Reward
The reward card is Extra Cursed Hazel Pigrum.