Half of damage dealt to this character is ignored.

•04-23-2013 Article: Seemingly a very simple power, but with an interesting twist. Since Invincible doesn’t reduce damage, any power that deals penetrating damage (like Penetrating/Psychic Blast or Exploit Weakness) will still be affected by Invincible. 

•04-23-2013 Article: It is also important to note that you always round up in Heroclix unless otherwise stated. Since Invincible lets you ignore half the damage it means that a character with a Damage value of 1 will deal 0 damage to the Invincible character – half of 1 is 0.5, which is rounded up to 1, so the Invincible character would ignore 1 damage. By the same logic, if the Invincible character is dealt 3 damage it would ignore 2 damage and only take 1 damage and so forth.

•04-23-2013 Article:At this time, the only strategy your opponent has to address Invincible is something like Pulse Wave, which allows powers to be ignored. 

Read more: http://heroclix.com/heroclix/a-whole-new-world-invincible-and-empower/#ixzz2RIRGzD1M

•All partial values, in HeroClix, are always rounded up.

 Example: You deal 7 damage to a character with Invincibile. Remember, half the damage (3.5) is ignored... but we round that up! So 4 damage is ignored!