Invincibility (not to be confused with the secret "Invulnerability") is a dark power used in Jak II which enables Jak to be invincible while in dark mode. The gift requires that Jak bring 200 skull gems to the oracle at its hut in the Water Slums.
As its name implies, Dark Jak is invincible to most forms of attack, with the exception of the beams fired by the aquatic sentry robots in Haven City's outer perimeter. He is also still susceptible to some hazards, including drowning (when the player gets stuck under an object trying to emerge from underwater), lava, dark eco pools, far drops, and bottomless drops. Invincibility is nearly identical to the game's "Invulnerability" cheat, except that it allows Dark Jak to knock back enemies just by colliding with them (though this does not actually damage them).
Similar to Dark Giant, this dark power is not present in Jak 3. It is unknown why he loses this ability. (However, the secret can still be purchased during the third game).