Rod of Keeper of the Void

This staff mutters and whispers softly, almost beyond hearing, with ancient secrets and tales of unknown stars. Attuned to by one who comprehends the Void, it grants a +1 bonus to spell attack rolls and spell saving throw DCs. It also allows one to regain one warlock spell slot as an action once per long rest. Inexplicably, while underground, the bearer of this item always knows the item’s depth below the surface and the direction to the nearest staircase, ramp, or other path leading upward.