Arkham Orb (5e Equipment)
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Wondrous item, legendary (requires attunement by an evil spellcaster)
The Arkham Orb is a bejewelled orb which must be held in one hand/tenacle/appendage/etc for its properties to be used:
It acts as spellcaster focus.
It provides +2 to spell attacks.
It increases user's spell save DC by +2.