I'll just... go ahead and answer the unanswered questions.
Which Great Beasts were responsible for masterminding the First Devourer War?
Kovo, Gerathon, and (secretly) Halawir.
What does the Copper Falcon do?
Enhances your vision in the books. In the game, I believe it gives +20% ranged damage.
What is the Evertree and the Wyrm's connection?
I'll admit, this one feels tricky. The roots of the tree temporarily imprisoned the Wyrm, but eventually it broke free and managed to damage part of the tree somehow. Also the Evertree was noted for keeping the balance of the spirit animal bond, but technically it was the Wyrm that created bonds.
Next question: Which Great Beast did Halawir secretly persuade not to join the Four Fallen in the first war?