The Undying

The Undying has a +2 bonus to all his Everliving rolls. In addition, the Undying's unit, and all friendly Immortals and Necron Warriors within 24" of him, have the Fearless special rule.

Independent characters can join other units.  They cannot, however, join units that contain vehicles or Monstrous Creatures.  They can join other Independent Characters, though, to form a powerful multi-character unit!  Independent Characters pass Look Out, Sir rolls on a 2+. A unit that contains one or more Independent Characters does not need a double 1 to Regroup if reduced to below 25% of its starting numbres, but instead tests as if it had at least 25% remaining.

Full details in BRB. Rule too long to copy verbatim.

When a model with this special rule suffers an unsaved Wound, it can make a special Reanimation Protocols roll to avoid being wounded. This is not a saving throw and so can be used against attacks that state 'no saves of any kind are allowed'. Reanimation Protocols rolls may even be taken against hits with the Instant Death special rule, but cannot be used against hits from Destroyer weapons or any special rule or attack that states that the model is 'removed from play'.

Roll a D6 each time the model suffers an unsaved Wound, subtracting 1 from the result if the hit that inflicted the Wound had the Instant Death special rule. On a 5+, discount the unsaved Wound - treat it as having been saved. Certain special rules and wargear items can provide modifiers to this dice roll; these are cumulative, but the required dice roll can never be improved to be better than 4+.

If a unit has both the Reanimation Protocols and Feel No Pain special rules, you can choose to use one special rule or the other to attempt to avoid the Wound, but not both. Choose which of the two special rules you will use each time a model suffers an unsaved Wound.

Units containing one or more models with the Fearless special rule automatically pass Pinning, Fear, Regroup tests and Morale checks, but cannot Go to Ground and cannot choose to fail a Morale check due to the Our Weapons Are Useless rule. If a unit has Gone to Ground and then gains the Fearless special rule, all the effects of Go to Ground are immediately cancelled.