What is Iron Shard?

This iron shard, like the ones implanted in the Guardians and the one Tonkee tries to steal from the geode’s control room represent evil or the enemy. These shards are a way that Father Earth, or the Evil Earth, has devised to allow Guardians to keep an eye on their charges. The shards also punish the Guardians with pain if they go against the desires of the earth.