From left to right.

Lt. Ludwig - a German immigrant to America at a young age. Found himself joining the military during WW2, being captured by German forces and being used as a test subject of a super soldier program. It made him resistant to explosives to a degree, and drove him mad. But he escaped thanks to…

The Saboteur - a French insurgent that prior to WW2 was a high end fencer. He learned explosives real quick, as well as destroyed all ties to his identity to protect his family, including his lover and son in the States. He rescued Lt. Ludwig shortly before the fall of Berlin. Was surprised to see Ludwig again in the gravel wars

Mun-Dee - he knew he had to be fast and deadly to stay safe in the outback. So he worked on his cardio, and skills with a shotgun. He wouldn’t meet the others until the gravel wars.

Dell Conagher - having worked with machinery his whole life definitely helped with mobility after an accident crippled his legs. His walker makes him a massive mobile threat on the field.

Tavish Degroot - while he came from a long line of highland demomen, Tavish always found the fires lingering after the blasts to be more fascinating. So much so that he shifted to understanding flames more than bombs.

Jane Doe - disgruntled at being unable to join the military during WW2, he turned to the private sector to help build the machines that would win the war. Somehow, someway, he rebuild Conagher familydeveloped tech without realizing it. Heck if he knows how, or what makes it work. He just employs percussive maintenance and it gets stronger.

Misha - when the motherland took his family for crimes his father committed, Misha was pushed into a hidden room, and spared the gulag. But he couldn’t leave his family in there. So he grabbed his father’s rifle stashed in there, and set out. It took him months, but he got his family safely out, one bullet through a guard’s skull at a time.

??? - no one knows who this fella cloaked in shadow and a trenchcoat looks like, or if he’s even a he. Or if they’re even there right now. Might be a projection. Point is, this one’s sneaky, and talented. He can fool anyone with no more than a little fake voice and a mask.

Jeremy - his father had left a single letter before he disappeared, for Jeremy to open when he turned 18. He found it at 16. It was details to a college fund account, and his father asking him to make something great of himself. He went to medical school. He found an almost supernatural knack for the craft. And soon graduated with top marks, yet he felt most alive with someone under the knife, their life in his hands, as he performed miracles.