Lief, Barda and Jasmine was in a posession of a jar of fire beads bought from Tom on their journey to the City of the Rats
Later, on King Lief, Jasmine and Barda's quest to find and destroy the Sister of the West, Tom sent them another jar of fire beads
A fire bead is a product sold at Tom's shop usually in bulk. It is a small round bead that bursts into flame and burns for a time when hit with a hard object or thrown with some force. The fire needs no additional fuel, but it will consume any flammable material it comes in contact with.
City of the Rats
Fire beads were among the many wares Tom showed Lief and Barda at his shop. The customers were originally not going to buy the fire beads, but after Tom saw their recognition of the Resistancesymbol, he gave them the beads for a lesser price.
When they had crossed the River Broad, Lief used fire beads to light a cooking fire on the Hira plain, but he, Barda, and Jasmine were quickly overrun by Plains rats. Throughout the night, Lief used fire beads to create a wall of flame along the riverbank, preventing the rats from reaching the companions. When morning came, there were a few beads left in the jar.
When facing Reeah in the City of the Rats, Lief threw the jar containing the remaining beads at the snake but missed, sending the beads crashing into a wooden pillar and starting a fire that eventually ravaged much of the city.
Isle of the Dead
Tom sent Lief, Barda, and Jasmine a jar of fire beads and a bag of Peppermint Fancies wrapped in a paper parcel. Lief started a campfire with the beads and burned the paper, revealing Tom's hidden note regarding his sister Ava.
Fire beads function the same way in the anime as in the books. However, they are not used to burn down the City of the Rats during the battle with Reeah, since the companions used nearly all of them to fight off the rats the night before. Instead, Reeah itself destroys the city when Lief knocks the Opal off its crown.