So I ran into Bull's old write-up for Highlander in SR3, and decided to convert it to 4a.
Immortal (Quality) 25bp
This quality grants the character access to Adept powers, as well as granting Immortal Regeneration, Immunity to Aging, and Immortal Detection. It also grants the Sensitive System quality. They may also use Weapon Foci like an Adept, and use the Assensing Skill if they have the Astral Perception power.
Immortals begin at base Magic 1, and may only increase this by defeating other Immortals. Immortals may not Initiate, but may have Magic scores higher than 6, and therefore PP higher than 6. For metamagics (purchased as powers) based off of Initiate grade, use half the Immortal's Magic (rounded up)
Each point of Magic higher than 6 enables an Immortal to add 1 to his attribute cap in his absorbed foes' highest unaugmented attribute. In the event of a tie for highest, the player chooses.
Immortal Regeneration
As Regeneration, except for the following: Immortals regenerate even from death unless their head is severed. Immortals have infinite overflow boxes, and automatically stabilize on Regeneration checks. They cannot regrow lost limbs.
Immortal Detection
Immortals can always sense their own kind, at a distance of Magic x 10 meters.
Non-Immortals who Assense immortals can't quite determine the nature of the aura, and take a -8 penalty to Assensing tests to determine the target's nature. Each Assensing of a different Immortal, which has 4 or more hits, reduces this penalty permanently by half, from -8 to -4 to -2 to -1 to 0.
Quickening
The Quickening lasts a number of rounds equal to the dead Immortal's Magic. The victorious Immortal suffers (defeated Immortal's Magic)S damage, resisted by Willpower, but also gains 1 point to his Magic rating. An area equal to the defeated Immortal's Magic x 10meters is filled with an electrical field dealing (defeated Immortal's Magic)Se. This is not cumulative with that taken by the victorious character.
Additional Immortal Adept Powers
Weapon Concealment (1pt)
The character can hide swords, clubs, and similar weapons under baggy or long clothing as if they had an additional -8 Concealability modifier.
Immortals may also learn the Masking, Adept Centering, Attunement (Melee Weapon), Psychometry, and Sensing Metamagics as 1 point powers.