The Obol is an object of great importance, stashed away somewhere in each zone. One will be hidden in each zone, placed within one of the levels in an obscure location. Should you find it, you will be transported to an extra level for the zone.
The additional level will be grueling and spooky. It will be a darker, more hazardous version of the third level of the zone, populated by 3 top-variant enemies, and Spookfoot Freak, once enough time has passed. Extra skeleton-themed props will also be around.
An exception to the bone-themed reskin of the third level pattern is the Sepulcrypt's own Bonus Level which instead follows a shadowy floating island theme.
The Doubol is an Obol found within the extra level, which grants the player access to the Boss Level of the zone. The Boss found within will be determined by the zone, though special alternate bosses may appear, either by random chance or from certain items.