Riot has published some story behind Uzgar the Ancient, a Freljord card from Call of the Mountain.
Uzgar the Ancient is one of the oldest trolls in Trundle's tribe, renowned for his savagery and legendary zest for battle. When butting heads with other trolls became too one-sided, he took on entire Freljordian villages at once–and never left with an empty belly.
Uzgar’s territory, won through sheer brutality, grew larger year after year until Trundle called a challenge. Though Uzgar had both the advantage of size and experience, Trundle managed to best him through trickery, causing an avalanche and trapping the larger troll.
Uzgar was just clever enough to know he couldn’t outsmart the new King, and called a truce through his growls. Ever since, Uzgar has gone to battle in the name of his king, knowing the biggest and best battles will be led by King Trundle.