NB: ArkhamDB now incorporates errata from the Arkham Horror FAQ in its card text, so the ArkhamDB text and the card image above differ, as the ArkhamDB text has been edited to contain this erratum (updated January 2022): Erratum: Corrosion's Revelation ability should read: "Discard Item assets from your play area and/or from your hand..." - FAQ v.1.2, Jan 2018.

Corrosion compels you to discard Item assets from play and/or from your hand until a certain threshold is reached. Whether or not you must discard 0 cost assets depends on whether or not you can reach this threshold:

• If you can reach this threshold, you may pick and choose which Item assets are discarded, and as long as the X value is reached, it doesn’t matter which ones are discarded. For example, if X was 5 and you had a 2-cost item, a 3-cost item, and a 0-cost item, you could discard the 2 and the 3 and be done with it. You’re not compelled to discard the 0-cost item.
• However, let’s say X was 6. In this example, you cannot reach the threshold, so you are compelled to do as much of the effect as you can. This will force you to discard 0-cost assets as well, as you attempt to resolve as much of the effect as you possibly can. Ouch!

Q: Can you discard Clasp of Black Onyx to Corrosion or Realm of Madness if you can't reach the discard threshold with other cards in hand? A: No, in this case, Corrosion would not discard the Clasp, because weaknesses cannot be discarded from your hand except when it is at random. Even if there are no other options for Corrosion to discard, the Clasp would remain in your hand.