Assassin is a Cosmic Encounter power from the Mayfair and Eon editions. Considered to be a classic power. Assassin gives the player the power to execute which “Removes Others’ Tokens”. What follows is the Mayfair text.

You have the power to execute. Whenever any other player's color comes up in the destiny pile, you must send one token of that color from any base to the warp. You select which token to execute. You assassinate a token of the player whose color was turned up, even if that player does not end up being challenged because of the Will or some other effect. On a Wild Destiny card, you may assassinate any token of your choice regardless of whom the offensive player chooses to attack.

History: After being subjected to colonial domination for thousands of years, a hive of Assassins rose up on an outpost planet in a forgotten empire. Devoted to terrorism and adept at choosing the most isolated and vulnerable as their victims, they mercilessly cleansed their sector of it overlords. Having become imperialists themselves, however, they learn new uses for their old talents.