Hydeker

Dr. Hydeker is a Shtriga, a monster that feeds on the lifeforces of the children. He was once hunted by John Winchester, and attempted to feed off of a young Sam Winchester. John managed to stop him from killing Sam, but Hydeker escaped and John lost track of the creature for years.

Background
In the Season 1 episode Something Wicked, Sam and Dean pose as CDC agents to investigate the sudden, bizarre illnesses of local children. They encounter Dr. Hydeker in the pediatric ward of the local hospital. He says no treatments have proved successful, and that their immune systems are compromised. As he investigates similar past incidents, Sam discovers a picture from the 1890s in which Dr. Hydeker appears. The brothers realize doctor is the shtriga they are hunting. Sam calls Dean, who is in the hospital near the doctor when he is informed of his true identity. He maintains his cover, but barely.

The brothers use Michael, a local boy whose brother is among the sick, as bait. They lure Hydeker and ambush him. During the fight, Hydeker starts to feed off of Sam again. Dean shot him with iron rounds killing him.

Season 1

 * Something Wicked