Bit of explanation on this mess;

Unicron and Primus are brothers, twins even, and polar opposites. Primus creates, Unicron destroys. Upon their creation, there was a third party, neutral, that was meant to tend to both of the brothers as needed once they had established Cybertron (before Primus made the Original Thirteen). Unicron stepped in, while Primus was busy, and wound up corrupting Izireyah, out of jealousy. She became his Priestess instead, and over time began to betray Primus, pulling Cybertronians over to serve Unicron instead. Among them, being the 'Fallen', from the Original Thirteen.

Aside from that, not too much there that won't get explained eventually?

Izireyah is copyright to myself, as an original character, but everything else is not.

The song is 'The One That Got Away' by The Civil Wars, found here
Primus' and Unicron's Bipedal design, in this drabble and any others with them, will be based off this artwork.