Rod of Absorption
This rod acts as a magnet, drawing magic spells of any nature (priest or wizard) into itself. It nullifies their effects and stores their potential until the wielder releases that energy as cast spells. The magic absorbed must have been directed at the character possessing the rod. The wielder instantly detects a spell's level, as the rod absorbs the spell's energy.
A running total of absorbed (and used) spell levels should be kept. For example, a rod that absorbs a 6th-level spell and a 3rd-level spell has a total of nine absorbed levels. The wielder of the rod can use the captured spell energy to cast any memorized spell, at a casting time of one, without loss of spell memory. The only restriction is that the levels of spell energy stored in the rod must be equal to or greater than the level of the spell the wielder wants to cast. With nine absorbed levels, the rod wielder could cast a maximum of one 9th-level spell, one 6th level and one 3rd level, and so on.
A rod of absorption can never be recharged. It absorbs 50 spell levels and can only discharge any remaining potential it may have after that. The wielder knows that the rod's limit has been reached upon grasping the item. Used charges indicate that it has already absorbed some of its maximum of 50 spell levels and that some of those have been used.
Here is a more specific example: A priest uses a rod of absorption to nullify the effect of a hold person spell cast by a wizard. The rod has now absorbed three spell levels and can absorb 47 more. The priest can cast any memorized spell of 1st, 2nd, or 3rd level, without memory loss of them, by using the stored potential of the rod. Assume the priest casts a hold person spell back at the attacker. This spell is only 2nd-level for the priest, so the rod holds one spell level of potential, can absorb 47 more, and has disposed of two charges permanently.