No I am not familiar with Iluvatar. Do tell more. Preferably the bold, I want to know more about Akallabeth and the Destroyer of Numenor.
Iluvatar is the destroyer of Numenor. Akallabeth is the name given to that land in Adunaic, the language of its people after its destruction: meaning "She that is/has fallen."
Numenor was an island in the West very near to Valinor, the Undying Lands where the Valar dwelt. It was a land gifted to men and women for their part in standing against Morgoth. After Morgoth's defeat, their power grew immensely but they were forbideen from going west because as mortals they weren't allowed to bring death to the Undying Lands.
So the only direction they could go was East, to Middle Earth. One of Morgoth's lieutenants was still alive and active in Middle Earth named Sauron. Numenor's army was so massive though that when they smote the gates of Barad-dur (Sauron's dark tower) he came forth and humbled himself to the king, Ar-Pharazon. In order to make sure Sauron kept his promise, he brought Sauron with him back to Numenor... which was a terrible mistake.
Over time Sauron used subtle arts to convince people that the Valar were only keeping them out of Valinor because they were jealous and afraid, and that it was man's destiny to claim the throne of the Undying Lands and become immortal himself. (But this was a lie, death was a gift to man from Iluvatar himself -- it was twisted and made to be thought of as a curse by the lies of Morgoth before)
Eventually Sauron convinces Ar-Pharazon to go to war with the Valar, a hopeless quest. Those still faithful to the Valar took ships to Middle Earth on the day of the attack, and the navy of the Numenoreans was the greatest navy ever to set sail. Seeing their approach, Manwe despaired -- not because of their military might but because they would betray him, and he asked Iluvatar for guidance. Iluvatar split the land asunder and the oceans swallowed Numenor and the Numenorean navy whole. Ar-Pharazon himself did set foot on the Undying shores, but he was swallowed by the earth, there to wait until the last day of the last battle when the Dark Lord is defeated at last.
The survivors of Numenor founded the kingdoms of Arnor and Gondor in Middle Earth. Aragorn, son of Arathorn, is a descendent of that line. So is Elrond half-elven (rather, shares descendents with that line).