Arcane Properties

One charge per day, which resets at dawn. As an action once per day, you can willingly suffer 1d6+4 HP in order to supply the onyx with one additional charge.

The following uses 1 charge:

Use your  bonus action to cast Banishing Smite

Notes: Overt value: 75 gp. Covert value: 5,500 gp. Sometimes knowingly and sometimes not, monstrosities are drawn to the onyx and anyone who bears it.