A giant underground snake that slumbers the majority of its life. When stirred, however, they prove deadly more often than not.

Your detour culminates in an extraordinary discovery: asleep in a shallow pool within an enormous cave lies a bolla, a snake as large as a Dragon. - Backstory Codex - Doomed (RPA-BC) 

Because of their size, bolla must sleep to conserve their energy, but will lash out with fangs when provoked; Though they spend almost their entire lives in hibernation, upon waking, they are known to be deadly.

You kick dirt into the bolla’s eyes, and it springs to life, striking you with its fangs. - Backstory Codex - Doomed (RPA-BC)

Bolla blood is ochre in color.

You fight valiantly, and soon the statues of the gods are drenched in the serpent’s ochre blood. - Backstory Codex - Doomed (RPA-BC)

Bolla eggs are filled with a yellow fluid that surrounds the snakelet;

Carefully removing it from your pack, you notice that it is now warm to the touch. Some sort of yellow mucus has begun to ooze from a small crack in the shell. The bolla appears ready to hatch. - Backstory Codex - Doomed (RPA-BC)

When departing from the path to Undercity at the Graveyard, you find a sleeping bolla:

• Wake the creature to fight it valiantly; Zalic witnesses your bravery, and the serpent escapes.
• Kill the bolla in its sleep; Zalic finds you triumphant and you find an egg.

If you kept the egg, it will be ready to hatch during your time in Kulbak Prison:

• Allow the bolla to hatch, and impress the other inmates.
• Hand off the bolla to a prison guard and gain a bribe.