Draconic soul transfer

Upon casting this spell. You chose 1 creature within your sight to siphon their hit points to equal 4d8 necrotic damage. The creature must make a constitution saving throw of 14 to avoid damage. You choose a second creature within your sight that will gain the same hit point amount equal to the 4d8 of necrotic damage inflicted on the first creature. 

Upon a successful spell the first creature has a visible smokey bright purple light pour from the eyes, and mouth and race to the second creature to transfer the hit points taken.