Eye of Judgement is a post-Moon Lord summon-like weapon.
In order to obtain it you need to bring all the materials written in Research Note #4 along with the Note itself to the Explorer. A special dialogue option will appear.
You need to bring :
Endlessly generates sharp bones, which will home onto enemies while you hold this.
Creates 8 homing bones on cursor position on use.
Doesn't take minion slots. Can be combined with other minions.
33% chance to reduce damage taken by player to 2 hitpoint.
Reduces player's endurance by 33%.
Can be enchanced into Eye of Pure Judgement