Soul Shards 1

SoulShards is a mod created by ShadwDrgn. This mod adds Soul Shards to the game, allowing players to kill hostile mobs and 'trap' their souls; mob spawners may also be absorbed with the Soul Shard. When a Soul Shard has enough charge, it may be placed in a Soul Cage to create a spawner; the Soul Cage will react depending on the tier of the Soul Shard put into it.

To level a soul shard up, you have to kill entities of the soul shard's type, or destroy spawners of the type.