TFA: Deals With Our Devils, Filler 1: The Marks and Meanings Behind them
When the entity known as the devil gave optimus his abilities he said that he would have power over the dark creatures of old, that means that he would have some of the abilities of the evil entities in the multiverse. However, he can only activate up to three marks at a time.
The omega symbol on his right shoulder symbolizes the Greek god Zeus, and Zeus aka Alex mercer from the prototype games. However, it takes a lot out of him, and he starts to go crazy with emotions of hunger, rage, and bloodlust at times. He can change his appearance of that which he consumes and mimic abilities.
The bat mark with an arrow through its heart represents vampirism, with abilities of alucard from Hellsing and Dracula from Castlevania. Although he is weakened by sunlight and a steak through his spark. He can levitate, control darkness, fly, and have enhanced speed and strength.
The symbol of a man being stuck by lightning is symbolic of titan shifting abilities from the attack on titan universe, however he can only activate one every five minutes.
The dragon symbol is the nine circles and torments of hell with the serpent at the center of all of them, this represents Dante's inferno, ("The anime not the game"). He can form a templar fashioned sword, a reaper scythe, a devil's whip, and a fiery pitchfork.
The mark of the sword symbol is basically the devil may cry insignia of date's sword rebellion. He can gain weapons from fallen, higher class demons and entities, as well as activate devil trigger. However, he is weakened to more powerful demon's auroras unless he defeats them in hand to hand combat.
The visor symbol is the doom marine's essence from the game doom. He can gain armor, speed, strength, and regeneration, but goes out of control at times.
The cross symbol is the one symbol that the devil didn't assign to Optimus. This symbol gives him some holy powers like an archangel knight. He can rain fire down from the sky, blind enemies with pure light, and fight on equal footing with those like the heralds of unicrn. However it doesn't last long, only about a minute or two at most.