The Bombinomicon is a badge item wearable by all classes. It is a leatherbound and twisted-looking tome with glowing red eyes and glowing red gums, with a team-colored Demoman class icon on its "forehead". A large, bloodstained circle of jagged teeth in the center of the cover clutches a cartoonish bomb. A player that dies wearing this badge will be gibbed in a spectacular purple or gold explosion.
This badge is awarded to players who have earned the Dive Into a Good Book achievement by traveling to Loot Island through the portal that appears after MONOCULUS is defeated and collecting the Bombinomicon held within a cage there. The Bombinomicon can be awarded to multiple players who complete the listed specifications. Unlike many Halloween items, the Bombinomicon is not holiday-restricted. The explosion effect will appear regardless of time, however it will change based on the current day. During a full moon or Halloween, the explosion will be purple, while any other time during the year, the explosion will be gold.
- The Bombinomicon was added to the game.
- [Undocumented] Updated the distortion effect on the Bombinomicon.
- [Undocumented] Updated the Bombinomicon effect to use golden particles outside of Halloween.
- The Bombinomicon no longer shakes the screen and has a delay before the explosion so that Snipers, Spies, and others can get better feedback on the actual cause of death
- The explosion effect still occurs when killed by a weapon that produces its own unique death effect: the Golden Wrench, Your Eternal Reward, Saxxy, Cow Mangler 5000, Righteous Bison, Short Circuit, Wanga Prick, Pomson 6000, Manmelter, Phlogistinator, Spy-cicle, and Neon Annihilator.
- No explosion occurs for feigned deaths.
- If a player who does not have the Bombinomicon equipped is killed and leaves behind a ragdoll, then equips the Bombinomicon before respawning, the ragdoll will explode when the player respawns.
- The name "Bombinomicon", a portmanteau of Bomb and Necronomicon, is a reference to the fictional grimoire from the The Evil Dead films which also had a face, was bound in flesh, and inked in blood. The name of the book from the film series was taken, as a tip of the hat, from the works of H. P. Lovecraft, which feature a grimoire of the same name.
- The Bombinomicon in the Underworld of Eyeaduct, the Island of Ghost Fort and the Hell of Helltower have text written on the back, along with a discount price tag of $6.66, and the spine listing it as the 15th edition. The text on the back reads as follows:
- There are hidden images inside the pages of the Bombinomicon in Eyeaduct showing a monster wearing the Demoman grenades in a circle and other assorted Demoman and bomb-making paraphernalia.
- Merasmus and Bombinomicon are voiced by the same voice actor, Nolan North.