Focus of Absorption

very rare (requires attunement)

While holding this focus, you can use your reaction to absorb a spell that is targeting only you and not with an area of effect. The absorbed spell's effect is canceled, and the spell’s energy--not the spell itself--is stored in the focus. The energy has the same level as the spell when it was cast. The focus can absorb and store up to 50 levels of energy over the course of its existence. Once the focus absorbs 50 levels of energy, it can’t absorb more. If you are targeted by a spell that the focus can’t store, the focus has no effect on that spell.

This can only store actual spells cast, not effects produced by innate spellcasting or other sources. These effects must have come from spell slots--a mind flayer's psionics or a monk's ki cannot be stored.

When you become attuned to the focus, you know how many levels of energy the focus has absorbed over the course of its existence, and how many levels of spell energy it currently has stored.

If you are a spellcaster holding the focus, you can convert energy stored in it into spell slots to cast spells you have prepared or know. You can create spell slots only of a level equal to or lower than your own spell slots, up to a maximum of 5th level. You use the stored levels in place of your slots, but otherwise cast the spell as normal. For example, you can use 3 levels stored in the focus as a 3rd-level spell slot.

A newly found focus has 1d10 levels of spell energy stored in it already. A focus that can no longer absorb spell energy and has no energy remaining becomes nonmagical.