Concept and Creation
Sentinel is created by Rob Liefeld. Sentinel was one of the original members of Youngblood since 1987 in Megaton Comics before he reappears in Image Comics in 1992. According to a promo, Sentinel could have pursued a highly successful career in genetic research with someone named Sonik before joining Youngblood.
When Marcus Langston was first approached by the U.S. Government in 1981 to develop a highly advance exo-skeleton for combat, he jumped at the chance. Unbeknownst to him, his involvement with the exo-skeleton would not end with its creation. As Sentinel, he combines his brilliant intellect with the awesome physical power afforded by his battle suit as leader of Team Youngblood, Youngblood's elite team for international crises.
In one mission, Sentinel lost his right eyeball in combat.
It's revealed that he is happily married to a woman named Elizabeth Hughes
In the miniseries Judgment Day, it was revealed that Marcus owned the Book of All Tales, a magical book that could alter reality and change people's fates. Marcus' fate was originally he had been headed for an early death as a thief, but he rewrote his destiny inside the book to make himself a superhero of an increasingly violent world. When Youngblood teammate Riptide discovered that Sentinel stole the book from her father, Storybook Smith, Sentinel murdered her and framed Knightsabre to cover his tracks. The truth behind Riptide's murder was eventually revealed in superhero trial when lawyer Toby Tyler discovered the book at his home and was taken into Supreme's custody in the Hell of Mirrors at his Citadel Supreme.
Alan Moore's Youngblood
Sentinel eventually escaped along with Supreme's rogues Televillain, Korgo, Shadow Supreme, Slaver Ant, and Vor-Em. Sentinel wanted to reclaim his leadership of Youngblood after his shame and when he discovered that Waxely Doyle is now funding the new Youngblood team, Sentinel formed Badblood consisting of Lounge Lizard, Satana, Speedwall, Poppy and Atomo to destroy his former comrades. They almost succeeded until Waxely came to Youngblood's rescue.
Since Sentinel's unfortunate breakdown and removal from Youngblood, there have been at least three or four successors who have took up the mantle:
- Brett Butler
- Sentinel 2.0 (unknown...possibly Kiesha)
- Kiesha Langston (Marcus' sister, also called Lady Sentinel)
- Dolante Murray