Bloodstar

6th-level conjuration (hemomancy)
Casting Time: 1 action
Range: 120 feet
Components: V, S, M (a ruby carved in a spherical shape worth at least 100 gp and a clay pot and marble dust)
Duration: Concentration, up to 1 minute

This spell creates a spherical magical object on a point you choose within range, known as a bloodstar. The bloodstar is a magical object in the shape of a 20-foot radius sphere that has AC 20, 50 hit points and resistance to nonmagical damage. The bloodstar pulses with ruby light, shedding bright light in a 20-foot radius and dim light for an additional 20 feet.

When you cast this spell, you can designate any number of creatures to be unaffected by the bloodstar. In addition, you can use a bonus action on your subsequent turns, to move the bloodstar up to 60 feet.

The first time each turn a creature with blood within the bloodstar's bright light radius takes damage from a source other than the bloodstar, its life force is drawn towards the blood star in a red stream. The creature must make a Constitution saving throw, taking 2d10 necrotic damage on a failed save, or half as much damage on a successful one. If the save fails, the creature's hit point maximum is reduced by an amount equal to the necrotic damage taken. This reduction lasts until the creature finishes a long rest, and the creature dies if this effect reduces its hit point maximum to 0.

Whenever a creature you chose to be un-affected by the bloodstar casts a spell within the radius of its light, you may allow them to siphon its life as a part of casting a hemomancy spell. If they use the amplify feature of a hemomancy spell, they may expend 10hp of the blood star in place of a hit die, up to pb "hit die" at a time this way.

Amplify 5. Each time a creature takes necrotic damage from the bloodstar, the bloodstar regains hit points equal to the amount of necrotic damage taken.

At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, the damage increases by 1d10 for each slot level above 5th.