Crusader is actually a Skrull named Z'Reg who came to Earth and was first ordered to spy the humans for an impending invasion. It was however then that he found out about the beauty of the planet earth and also became friends with a newbie hero named Freedom Ring. Z'Reg trained the new hero how to cope with his newfound powers and the hung out a great deal. After Freedom Ring died, Crusader took his Power Ring in remembrance of his young friend for that was the "Skrull way" when a fellow brother died.
Crusader was created by Robert Kirkman and Andy Kuhn and first appeared in Marvel Team-Up Vol.3 issue 20 (2006).
Major Story Arcs
Becoming a Hero
Most likely because of the loss of his friend and in remembrance to him, Z'Reg became the hero known as Crusader. Some time later, he even helped the Avengers fight the villainous Titannus. The Avenger Captain America (Steve Rogers) took notice of his fighting skills and was impressed by the young heroes methods.
Joining the Initiative
Crusader joined The Initiative in the hopes of getting a registration card. Crusader was accepted in the program and was located at Camp Hammond, the training-ground for new recruits. It was on one day that Crusader noticed that Camp leader Yellowjacket (actually a Skrull named Criti Noll posing as Hank Pym's alter ego) ate strawberries and pickles. He noticed this because these were a good substitute for a famous Skrull food, so both Crusader and Noll were eating it. When they ran into each other, Crusader saw Noll's food choice first, and realized he was a Skrull. Not wanting Noll to know HE was a skrull, Crusader used the Freedom Ring to change his meal into grapefruit. Crusader did not know how to reveal Noll without everyone seeing he was a Skrull and attacking him, so he kept his mouth shut.
Secret Invasion and Death
In the story arc " Secret Invasion" Crusader took the human's side, though they did not know he was a Skrull. Proving himself a worthy hero to the planet Earth, he was even complimented by Nick Fury of the Secret Warriors. At the end of the Secret Invasion Story arc, Crusader was the one who fought and killed Criti Noll, who had been impersonating Yellow Jacket. During the fight, it was revealed that Criti did not know he was a Skrull either. After the war was over many heroes including Gravity were congratulating him when 3D Man shoots him in the head simply saying "What?". Though while on the ground dying, he looks back wishing it could all have ended differently when he suddenly disappears.
Aside from the standard Skrull powers of shapeshifting and regeneration Crusader has a power ring called the Freedom Ring, which is made of a fragment of a cosmic cube. It grants limited reality warping.