Omen of Monstrous Might - Item Raises Monster Levels

I would like to propose to GGG a new item that when placed in your inventory would make monsters spawn at higher levels that depends on monster rarity, thus making them grant additional XP. This would be a new non-crafting omen, much like Omen of Amelioration reducing XP loss upon death.

Omen of Monstrous Might
Drop Level: 1
While this item is active in your inventory, monsters you encounter will be of higher level:
* Normal monsters: +2 levels
* Magic monsters: +3 levels
* Rare and Unique monsters: +5 levels