Target opponent chooses a number. You may have that player lose that much life. If you don't, that player sacrifices all but that many permanents.
6/1/2005 After the opponent chooses a number, Choice of Damnations’ controller may choose to make that opponent either lose that much life or make that opponent sacrifice permanents.
6/1/2005 If the opponent must sacrifice all but a number of permanents, that opponent chooses that many permanents and then sacrifices the rest. If the number chosen is greater than the number of permanents the opponent controls, the player sacrifices nothing.