Energon is raw mineral found on many worlds that can be refined into three forms, the Omnicons mine and refine it into positively charged red energon, the Terrorcons make negatively charged green energon, this has to be established at some point explaining why a collision of both in huge quantities is a bad idea. The fourth form is blue ultra energon that gives transformers superior speed, fireblast, strength and a healing ability.
The Spark of Combination is a technological adaptation of the Autobots, it's designed to merge minds but has a physical advantage too.
Unicron is heavily damaged after Quintessa blew up in his face and he's gone into shutdown, creating Galvatron and the Terrorcons to restore him.
Alpha Quintesson is the Supreme leader of the Quintessons, a galactic empire that was destroyed by Unicron in the space between Armada and Energon, he's now seeking to restore his empire through Unicrons power. His people have a terrible reputation with the Transformers and often clashed with both sides and many other races at the height of their power. Despite their past reputation he's always been fair to outsiders and is an ally of Rodimus.
The Decepticons have settled in their new life, Megatron is resurrected and reformatted into Galvatron and straight off becomes a fanatic herald of Unicron, he is army building and uses Thrusts spark to restore Scorponok, then forces Cyclonus and Tidal Wave to become Snowcat and Mirage (also Snowcat is renamed Snowstorm), Demolisher is allowed to retain his identity due to loyalty but Starscreams lobotomised into a bodyguard and assassin. Galvatron eventually reverts to Megatron to stop Unicron. Shockblast is basically Shockwave except he's been mentally broken by Unicrons attack and is unstable, he's aware Megatron once changed him with a
robosmasher and wants revenge.
The Autobots are busy restoring Cybertron with the aid of the Omnicons, a massive group of Cybertronians like the Nails from IDWs comics, only they shed their allegiances. and have forbid the Autobots and Decepticons from visiting their worlds. Rodimus was the instigator of the Omnicons and ally of the Quintessons, he's morally grey to the Autobots. Some captured Omnicons are reformatted into Terrorcons and cloned.
Omega Supreme is an ancient guardian robot rebuilt and upgraded by the Autobots to fight the Decepticon and Terrorcon threat.
The Combiners are a trio of Supercons with Omnicon soliders, Barricade and Steamhammer are reprogrammed and join the Decepticons while Storm Jet remains an Autobot, they have a mastery of ultra energon.
Instead of Primus, we have Vector Sigma who consults with Optimus and gifts the Autobots with the spark of combination and ultra energon.
The Minicons have largely relocated to the Omnicon realm though some remain on Cybertron.