The Collaborative International Dictionary
Intervener \In`ter*ven"er\, n. One who intervenes; especially (Law), a person who assumes a part in a suit between others.
Wiktionary
alt. One who intervenes. n. One who intervenes.
Wikipedia
An Intervener is a person who works consistently one-to-one with an individual who is deaf-blind. Deafblindness is a low incidence disability that describes individuals with varying degrees of vision and hearing losses. The combined loss often compromises the ability to access information in the environment or to communicate effectively. Inverveners provide a vital link to the people, things and events in the world surrounding a deaf-blind person]. Interveners provide services in educational settings for students, as well as in early intervention and community settings.
Usage examples of "intervener".
For he knew at once what it was that the Interveners had been trying to avoid, and it wasn't the Christian conquest of Islam.
But he was right -- if he tested her knowledge first, he would know how deeply he could delve into the material that mattered, the new findings that he thought would answer the great question of why the Interveners had given Columbus the mission of sailing west.
After all, the Interveners did prevent exactly what they set out to prevent.
The Interveners had come to Columbus dressed up in the image of the God he believed in.