Mind Control Devices:

Hypno-Persuader: Used while it's victims are asleep, this device allowed Doom to hypnotize the Fantastic Four into believing they were losing their powers. The effect is not permanent and requires frequent treatments in order to maintain its affect on the recipient. Appearances: Fantastic Four #85 volume 1

Subliminal Inducer: Also used while the recipient is asleep, the Inducer has the ability program loyalty and obedience to whom ever it is used on. Doom used this device on Dr. Bruce Banner in order to take command of his skill in gamma technology and his alter ego, the Incredible Hulk. Appearances: Incredible Hulk #144

Remembrancer:

Fully aware that a direct heir was unlikely, Doom took on the orphaned Kristoff has his ward. Also aware that he would not live forever, Doom took steps to prepare for the eventuality of his demise. The Remembrancer was created so that Kristoff would have the benefit of all Doom's knowledge and be able to continue his work in the event of his death. Using memory tapes derived from Doom's own brain, these tapes would "play" and be "recorded" into a recipients mind. The only known use of the device was on Doom's ward Kristoff, and the attempt proved unsuccessful. The device was too strong on the child's mind and overrode his personality. Implanted with Doom's own ego and strong personality, the young Kristoff interrupted the procedure before completion. The resultant side effect was that Kristoff believed himself to be the real Doom and eventually came into a long conflict with Doom himself.

Appearances:
Fantastic Four #247