The main figure in Islam is?

He is not the "main deity". He is the Only Deity. The One God of Abraham. In Hebrew Eloha, in Aramaic (the language of Jesus) Alaha, and in Arabic Allah.

This is the only God that has ever been. No partners has He, and no offspring. He is not like His creation, and is not within His creation. He is beyond all creation and beyond all senses.

"Say He, alone, is God. The One upon whom everything completely depends upon - for everything. He does not beget offspring, nor was He begotten of anyone; and there is nothing at all like unto Him". Qur'an, Chapter 112

Muslims are the one people who refuse to worship anything other than the One God, alone.