Corrupting is a pickaxe enchantment added by Forbidden Magic. When a Corrupted pickaxe mines any Infused Stone, any of the seven Nether Shards (e.g., the Gluttony Shard) has a chance to be dropped in place of its regular shards.
This infusion has an instability of "Moderate" and consumes 6 XP levels.
The Nether is great and all, but it's also kind of a ... Hell Hole.
The Corrupting enchant allows you to harvest Nether Shards without having to be in the Nether. A pickaxe enchanted with Corrupting will randomly corrupt harvested elemental shards, changing them into nether shards. The shards only seem susceptible while they are encased in infused stone, so corrupting a shard cluster will have no effect.