Mortal Wound: (non-optional) When a character takes 3 or more damage from Sabretooth's attack, that character can't heal for the rest of the game even if this power is countered or lost.

Animalistic: Sabretooth can use Combat Reflexes and Super Senses.

What does it mean "takes 3 damage"?
In a nutshell, after damage is reduced by any potential game effect (maybe Sabretooth is attacking a character with Invulnerability) if the target ends up clicking its dial 3 or more times, it can't heal for the rest of the game.

So what happens then if Sabretooth attacks a White Lantern with the LIVE! special power? That power stops the dial from turning.
If the dial stops turning, then it stops turning. Simply count how many clicks you did turn it, and that is your damage taken and if that number is less than 3, Mortal Wound will not prevent healing.

For example, Sabretooth hits a White Lantern and would normally cause that character to take 3 damage. However, after clicking just 1 click, LIVE! appears in the slot and the dial stops turning. So the character only took 1 click and Mortal Wound will not prevent healing.

And, yes, if you've been playing Heroclix for more than a little while, this is a new ruling (as of the 5-15-11 PG).

So what kinds of healing does Mortal Wound prevent? And can I use the White Lantern special object to get around Mortal Wound?
All healing. Period. Mortal Wound does not name Support or Regeneration or any other specific method of healing, so any and all healing will be prevented by Mortal Wound.

And the White Lantern special object prevents Support and Regeneration from being countered. Mortal Wound does not counter anything, so the White Lantern will have no effect.

Wow. So how do I heal if this happens?
You don't. Since Mortal Wound specifies that it continues to function even if the power is countered or lost, not even defeating Sabretooth will remove the effect. Once wounded, your character(s) can't be healed at all during that game.

Wait, does this mean a character hit with Mortal Wound can't use Support on another character?
No, that's not what this means. Say character A was hit with Mortal Wound and can now use Support. Character B is also damaged (though not by Sabretooth) and would like to be healed by Support. Character A can be given an action to use Support; Support does not heal A. Instead, A will use the power on B and B is the one who is healed.

Updated to reflect latest PG (5-15-11).