This ring appears as a silver band with a dragon's claw holding a cloudy grey gem. When a monster is killed while the ring is worn the ruby will gain veins of blood red until the whole gem is filled red.  Stored blood can be used to do the following

After one creature is slain you can use the stored blood to gain 10 hp of temporary health

After 2 creatures are slain you can use the stored blood to create a 20ft tendril of blood that can restrain one creature within range

After 5 creatures are slain you can use the stored blood  to take control of one creature within 5 feet which requires concentration

After 10 creatures are slain you can expend all stored blood to create a simulacrum which your soul will be moved to once you die

stored blood that is not on the list is converted into a +2 to damage

Notes: Restrained