Unkillable
You cannot be killed! You are subject to all the other effects of injury. You feel pain, your wounds slow you, and you can be stunned or knocked out. You lose the use of any limb that receives a crippling wound, and you might even lose the limb itself. You can even lose attribute levels, advantages, etc. to disease, injury, or poison. However, you will only die if your body is physically destroyed – and sometimes not even then.
This advantage comes in three levels:
Unkillable 1: Injury affects you normally, but you need never make a HT roll to stay alive. You can survive (and even function, if you remain conscious) down to -10×HP, at which point your body is physically destroyed and you die. As long as you are alive, you heal at your usual rate – typically 1 HP/day, modified for any Regeneration you may have. Crippled limbs do heal, but severed limbs are gone for good unless you have Regrowth. 50 points.
Unkillable 2: As Unkillable 1, but you do not die at -10×HP. Once you reach -10×HP, you are reduced to an indestructible skeleton and automatically fall unconscious. You sustain no further damage from any attack. Once the damage stops, you heal normally – even if you’ve been hacked to pieces – and any severed body parts will grow back. You regain consciousness once you have positive HP. Note that your enemies can imprison your remains while you are unconscious, or even expose them to a source of continuous damage (fire is a common choice) to prevent you from healing. 100 points.
Unkillable 3: As Unkillable 2, except that at -10×HP, you become a ghost, an energy pattern, or some other incorporeal form that cannot be contained or damaged through normal means. At this stage, you fall unconscious and heal normally. Once you are at full HP, your fully intact body will coalesce in a location of the GM's choosing. 150 points.
With the GM's permission, if you have Unkillable 2 or 3 and are taken to -10×HP, you can trade in Unkillable and use the points to buy a spirit or undead racial template (if such things exist in the setting), becoming a ghost, revenant, etc. once you heal all your HP.
By default, you age normally, and will eventually die of old age. To be truly immortal, combine Unkillable with Unaging – and possibly one or more of Doesn't Breathe, Injury Tolerance, Regeneration, and Resistant.
Special Limitations
Achilles' Heel: Damage from one particular source (possibly one to which you have a Vulnerability) can kill you normally. You must make normal HT rolls to survive at -HP and below, and die automatically if this damage takes you below -5×HP. The limitation value depends on the rarity of the attack, as defined under Limited Defenses: -10% if "Rare," -30% if "Occasional," or -50% if "Common" or "Very Common."
Hindrance: A specific substance (e.g., silver or wood) prevents healing – whether by natural means or Regeneration – for as long as it remains in your body. Once you pass out from your injuries, you stay dormant until this substance is removed. The limitation value depends on the rarity of the substance: -5% if "Rare," -15% if "Occasional," or -25% if "Common."
Reincarnation: This is only available for Unkillable 2 or 3. When reduced to -10×HP, you recover at your usual rate, but you wake up in an entirely new body with new abilities. The GM creates the new form (or may allow you to do so), but you always retain the Unkillable advantage. -20%.
Trigger: This is only available for Unkillable 2 or 3. Once reduced to -10×HP, you require some substance (such as human blood) or condition (such as a ritual) before you will start to heal. Until then, you will remain dormant. The limitation value depends on the rarity of the trigger: -25% if "Rare," -15% if "Occasional," or -5% if "Common" or "Very Common."