The Forest God is a supporting antagonist of Hellboy II: The Golden Army. It is a giant elemental monster that served for Prince Nuada until its demise.
Following the death of Prince Nuada's right-hand accomplice Mr. Wink, Nuada decides to raise the stakes against Hellboy and his gang of fellow BPRD agents by unleashing the Forest God. To do so, he opens up a golden egg chamber, revealing a Forest God seedling inside. Commanding the Forest God to kill Hellboy, Nuada throws the seedlings into the sewers, where it grows up to giant proportions and started attacking Manhattan.
The B.P.R.D. agents are forced to fight back against the Forest God, but the latter was too strong. Johann Krauss suggests to Hellboy that he get to higher ground so that he can use his weapon to shoot the Forest God in the head since it happens to be its weakest point. Despite some difficulty in avoiding the Forest God's tentacles while rescuing a baby from danger, Hellboy was able to get to the top of a building and uses his gun (Big Baby) to shoot down the Forest God in the head twice. killing it for good. As the Forest God dies, its corpse consumes much of the area, covering it in flora and fauna, much to the shock and surprise of several witnesses.
Hellboy: Sword of Storms
Hellboy: Blood and Iron
Hellboy: The Golden Army