The entire area lies within the Sahara Desert. Western Kidal is sand and rock desert. That region's center is the Ifoghas Mountains(1); on their west side is a chain of oases. Eastern Kidal and western Agadez is the Talak Desert--a mixture of sand dunes, flat hard packed sand flats and paths for occasional flood waters. Moving eastward gets one to the Aïr Masif and then the vast sands of the Tenere of the Tafassasset. In the northeast are the Hamada Mangueni and Tchigai plateaus and south of them the Grand Erg (sand duen system) of Bilma. One of the two main routes across the Sahara goes through the eastern Talak and southern Aïr, marked across flats by rusty oil barrels with two-by-fours stuck in them.
Outside Agadez everyone speaks Tamasheq, the language of the Tuareg. There are some Hausa speakers in the departmental capital just like in all of Niger's cities. Everyone is a Sunni Moslem. Agadez, a small city, is the most significant settlement.
People have probably been in the area for nearly 100,000 years, especially considering the environment has been more hospitable in the past.
The Berber peoples--the ancesters of the Tamasheq--moved across the Sahara thousands of years ago.
The Hausa moved north from Nigeria, settling trade centers.
I'm unsure about how long after the Arab conquests the Tuareg of this area converted to Islam. Givern their nomadism which increased interactions northward it may have been quite early.
north
east
south of eastern Agadez
south of central and western Agadez
south and west of Kidal
northwest of Agadez and northest of Kidal
(1) 'Adrar' means mountains in Berber languages.