The Silvermote Company
Wondrous item, uncommon (requires attunement)
While wearing these bracers, a warlock can use their eldritch blast to manipulate the life force of those they target with their blasts. The bracers can hold the level of the attuned wielder + the attuned wielder’s proficiency bonus in a pool of temporary hit points. This pool is emptied each day, but filled by dealing damage with eldritch blasts.
The attuned wearer can expend hit points at a 1/1 ratio with a touch to deal necrotic damage, or heal hit point damage.
The attuned wearer can expend hit points at a 2/1 ratio to add necrotic damage to an eldritch blast, or heal a target hit by an eldritch blast.
Both of these uses are bonus actions added to a touch attack and eldritch blast attack action respectively.
The bracers do not have a cap on how much can be expended through them. Warlocks slain by overexpending their own hit points immediately owe a major soul boon to the blood demon Chagnomosh, who will require payment in form and time that suits an entity of such evil and eldritch power.