Upon approaching a dead PC, the item will be visibly pulsing red light.
Anyone can use their action to activate the Revivify spell imbued into the diamond.
As a favour to the Knights of the Realm, Winston imbued the diamonds with a Greater Healing Potion (4d4+4), which is activated with the Revivify spell.
Cannot be counterspelled, as no verbal or somatic components required
Susceptible to anti-magic fields