Note: I have made up names for the different headings just to organise the writing. They're not official or anything.
As a Guardian
You start talking with Aquila while in the air above Angel Falls. When this finishes, you see a girl (Errin) and her grandfather walking down a path back to the village. You also notice a Cruelcumber and two Slimes waiting to ambush them. You follow Aquila and enter a battle with the enemies. It is fairly easy, with Aquila on your side. After this, Errin, who is the only person who believes in the guardians, offers some benevolessence. Aquila then takes Hiccup back to the observatory. He leaves, after stating that Hiccup must go and see Apus Major to report. yup thats wright u fall in angel falls. ironic right?
You start by a star shaped blue hole in the ground, and go south towards a set of stairs, then up them and down the short, elevated corridor. You go up the stairs at the end and reach the right room. Then you go forward and talk to Apus Major. He will ask you if you are ready to do tasks on your own - say yes. After that he will tell you to visit Yggdrasil and offer your benevolessence. Go round the stairs and through the doors to the outside of the observatory. Climb the stairs until you get to the very top, and interact with the tree. You will offer your benevolessence, and then return to Apus Major. He will tell you to go below and gather more benevolessence. Go back to the star-shaped blue hole (the Portal), and talk to the Guardian there to be sent back to Angel Falls.
Back in Angel Falls
When you arrive back in Angel Falls, first go to the stable in the west of the town, and collect all the horse manure. The owner of the stable will then wake up and (without seeing you) thank you and give you some benevolessence. Next, find a women inside the church, who is praying for her husband's ring. Go to the dog at the east of the village, and talk to it (press 'a'). It will guide you to the ring. Pick it up and take it to the women. She will also give you some benevolenssence. When you exit the church again it will be night time. You will meet Aquila on one of the bridges, and he will tell you that a lost soul is roaming the village. Your final task is to talk to the soul. When you do this it will realise it is dead. You will obtain a benevolessence and the soul will leave the mortal realm. Go back to Aquila, and he will take you back to the observatory. Then go and offer the benevolessence to Yggdrasil. There will be a cut scene where the Observatory is attacked by some force below, and you are thrown off, and fall into the mortal realm.
(and did you know? i like CHEEZBURGERS)