What will be the mark of the Beast?
The mark of the antichrist is described in Scripture this way:
Rev. 13:16 And he causes all, the small and the great, and the rich and the poor, and the free men and the slaves, to be given a mark on their right hand or on their forehead,
Rev. 13:17 and he provides that no one will be able to buy or to sell, except the one who has the mark, either the name of the beast or the number of his name.
Rev. 13:18 Here is wisdom. Let him who has understanding calculate the number of the beast, for the number is that of a man; and his number is six hundred and sixty-six.
The Bible never specifies the way the number of the antichrist will be applied to the body, except to describe it as a "mark". The Greek word for mark is charagma, which means "to sharpen, to engrave; a stamp, impress". Therefore, the mark could be made in any number of ways, including a tattoo or other physical marking. Anything more is speculation.