How do I stop those fireballs?

Hint 1 of 7:

Remember those books you read?

Hint 2 of 7:

The talisman can neutralize the fireballs.

Hint 3 of 7:

Walk up to the tree-thing, while avoiding fireballs and the water monster.
Then put the talisman on the altar at the foot of the tree-thing.

Hint 4 of 7:

It's not over yet.  The tree-thing is still alive.