The black thing deep in your ear is often impacted earwax.
Impacted earwax can darken in color and turn black as it collects debris and ages.
In other cases the black thing deep in your ear may be a foreign object lodged in the ear or in some cases it may be a sign of a ruptured eardrum or other ear issue.
In most cases though the black thing deep in your ear is simply impacted earwax.
I had black impacted earwax in my ear before and I was able to remove it by using some earwax softening drops, although you can also use some mineral oil or hydrogen peroxide to help soften the earwax and help it come out easier.
If you're unable to get the impacted earwax out of your ear on your own, then you can see a doctor who can help remove the impacted earwax safely.
If you have a foreign object in your ear, then you may be able to use some tweezers to gently remove it if you can see it and reach it or have someone else use the tweezers to gently remove it.
Earwax is a natural substance that is produced in your ear canal to protect and clean your ear.
The earwax normally moves outward on it's own, although sometimes the earwax may build up and become impacted, especially if you use cotton swabs to clean your ears.
Having dark or black earwax is often a sign of impacted earwax, as it has aged and has collected more debris and even bacteria.
Symptoms of impacted earwax include earaches, a feeling of fullness in the ear, tinnitus or ringing in the ear and sometimes hearing loss if the earwax is really impacted.