A mind ruler is a cosmic entity that is a point and sentient. They like to seep into the minds of other cosmic entities and start controlling their minds. First, the pesky little things will slowly absorb the knowledge of the subject. If it's a basic life form, like Dave, the mind ruler will only take about a few seconds before the thing is finished. If it's a more advanced life form, for example Cosmic Dominators, knowing how to cooperate, bend space to make their Cosmic Burrows, and even make a replica of CROM if really needed, then the mind rulers may spend possibly multiple Earth years taking their knowledge. This explains why the subject starts to forget things in the process. When the knowledge is drained, the mind ruler takes control.
An anti-controllant is a cosmic entity that also seeps into a cosmic entity's mind but will restore knowledge from mind rulers back to the cosmic entity's mind and also kick the mind ruler out of the mind. These anti-controllants will also stay and duplicate throughout the entity's mind for extra security.