Legendary
Belashyrra's Beholder Crown
Symbiont
You can cast Necrotic spells up to Tier KEY even if you normally could not. Instead of mana, you take d10+5 damage for each tier of the spell (5 damage only for cantrips). If this reduces your HP to zero, you also take a Wound per 10 excess damage.
Once attached, a symbiont cannot be removed without a skilled surgeon. Each symbiont grafted gives you advantage on STR saves, disadvantage on WIL saves and you have 1 less Hit Die than normal. These effects stack. (1/Safe Rest) When marking your last Wound, roll a d4 for each symbiont (i.e. roll 2d4 if you have 2 symbionts). If you roll a 4 on any die, recover 1 Wound and 1 HP.