An ring to rule them all. An ring wich allows the bearer to break weak minded individuals and brainwash them, binding their will towards yours for an hour they will follow any command as you wish. After it they will just be extra docile towards the bearer and will do their bidding. You could for example create an army with it, subjects under the rings influence may betray you too after the 1 hour of total control, this is due to the ring letting them think and have their own mind to further increase the subjects intelligence, if per say this ring was modified to not do that the subject would be unable to think or even feel, and would act like empty machines. People with an iron will do not succumb to it 

Note: Dragons won't be affected by this unless they are low on health and the DM can always choose to have this, not have it or select wich creatures, characters have iron will

Notes: You require an attunement towards arcane arts and magic to be able to truly unleash its power