Martin

Now that the bag is out that he can't die, Martin fesses up to a few things. His name was Max Lee, he's about 60 years older than he told you. Most of the last 30 years was spent being a mercenary, his last mission was in the employ of Zaria, a micronized zentraedi who was a member of the RDF and used their funding and backing to start building her own private army/mecha. (Later RDF analysis would have shown that all the people under her original RDF command were exposed to a mutated plant that caused varying degrees of insanity, not sure if the PC's ever figured that out).

He 'died' in service to her attacking an RDF strike force at one of the outpost bases, taking several missiles which blew him to pieces. He glazes over most of the details here, leaving it at 'it hurt a lot'. When he eventually revived, it was several years later, the longest he'd ever been 'dead', since he usually regenerates in hours at most, usually minutes. Since his revival, he's traveled around North America primarily, working odd jobs (bartender his latest). He picked North America due to the limited combat (bandits etc), as he wanted to get out of the mercenary business.

He'll confirm that the guy in the base that he killed was immortal, as well as go over 'the rules'.

The Rules

All immortals must abide by the rules, or face nasty consequences. Immortals can only die if their head is severed, or in some obscure way that Martin only once heard about but never saw. “Rumour has it that two immortals were fighting it out, and a student of one of them jumped in and tried to help. His teacher won, but when the quickening was over, the student was dead too”. [Don't hit 0 Quickening Points]

Immortal battles must be one-on-one. [Any immortal that is in range when a duel concludes will lose some of their power.]

Holy ground is sanctuary. [All power released on holy ground is lost.]

Immortals are sterile, and can sense the presence of other immortals.

Legend says that immortals are fighting throughout time, and when the time of the Gathering occurs, the last surviving immortal will gain The Prize. No one knows what it is for sure, but it's generally accepted to be assloads of power.

[Brackets are me clarifying in-game effects to breaking the rules]