John Romero gifts 'Doom' 18 new levels for its 25th birthday

'Sigil' is free, but you can spend $166 on it if you'd like.

Ready to feel ancient? The original Doom is 25 years old -- and co-creator John Romero wants to make sure you know it. He's preparing an add-on for the 1993 game, Sigil, that serves as a "spiritual successor" to the classic shooter's fourth episode ("Thy Flesh Consumed") with nine single-player story levels as well as nine multiplayer deathmatch levels. The expansion will be free if you're just looking for some nostalgia-fueled demon slaying, but you can also spend a lot of money on it if you're determined to flaunt your fandom.

Sigil will also be available in a $40 Standard Edition that includes an elaborate box from metal album artist Christopher Lovell, a soundtrack from Buckethead and a 16GB USB drive themed like a floppy disk. If you're really, truly committed, you can drop a whopping $166 on a Beast Box that includes everything from the Standard Edition plus an autographed box, a pewter statue of Romero's head on a spike (for all the Doom II fans), a coin, a t-shirt and a Christopher Lovell art print.

Both the new levels and the physical copies are expected to arrive in mid-February. You can pre-order the boxed releases from now through December 24th. You definitely don't need to pay for Sigil. Consider this, though: outside of Doom Eternal, this is your best chance to mark the series' 25th anniversary with something tangible.