The Mark is a passive item.
A red marking of three 6s (the number of the beast, 666) making a triangle.
Isaac gets a mark on his forehead.
Will kill you if you have two or fewer heart containers from a deal with the devil despite giving you one soul heart; if it costs 2 health and you have 2 health you will die. If you have 1 health and it costs 2 health you will die.
- As a damage-up, it basically synergizes with anything in your run.
- From the Book of Revelation: "And I saw thrones, and they sat upon them, and judgment was given unto them: and I saw the souls of them that were beheaded for the witness of Jesus, and for the word of God, and which had not worshipped the beast, neither his image, neither had received his MARK upon their foreheads, or in their hands; and they lived and reigned with Christ a thousand years." (quote 20:4).
- The pickup shows the tips of the sixes meeting in the middle, however when the player receives the mark the bodies of the sixes are touching with the tails facing outward.
- The mark may be a reference to the British horror classic The Omen where Damien Thorn, the Antichrist and the son of Satan, has a mark of three sixes hidden on the top of his scalp.