Master Chief. John-117 is a SPARTAN-II soldier designed by the UNSC to combat the Covenant. He is cybernetically enhanced with superior strength and agility. His first appearance was in Halo: Combat Evolved in 2001.
Master Chief would fit in well for an adventure that takes place in the Astral Sea or Astral Plane. Depending on your specific world, he could be considered a traveler from the future or someone trapped in the fantasy world of Faerûn.