GGG has not officially clarified whether there is a similar item level restriction for Ancient Orbs. In practice, though, Ancient Orbs apparently are allowed to reroll low item level unique items to into higher drop level items. It is rumoured that this feature of Ancient Orbs can be used to eliminate undesired uniques in order to have a slightly higher chance to roll Headhunter.

Reforging a unique item means the base item type can change when the orb is applied. Ancient Orbs do not change the inventory size of an item, so 2x4-sized "tower shields" for example stay within that group. Unique cluster jewel are in the same group in other 1x1 jewel as well. It is worth noting that using Ancient Orb will remove any influences, as well as remove enchantments from the item.