Summer's End/Quick guide

Luring the beast

 * Talk to Summer at the wilderness wall, north-east of Varrock.
 * Enter the portal
 * Operate Jennnica's ring while standing on the portal.
 * Run north to the dungeon, collapse the entrance.
 * Return to the spirit realm.
 * Run north and lure the beast to the entrance with your blue charm familiar. Enter the cave before it has a chance to consume your familiar.

Inside the cave

 * Avoid the beast's ranged attacks by moving away from the missiles.
 * Run north and cut 15 logs from the wall.
 * Once you have 15, light 3 fire pits (5 each).
 * (Optional) Restock your food and return to Summer to continue.

The dark core

 * Enter the next room.
 * Avoid the missiles like before.
 * Soon a dark core will appear, dig a hole in the soil and lure the core into it.
 * Repeat this 3 times.

The coloured graves

 * Watch carefully which graves the coloured spirits enter.
 * The beast will charge a coloured attack, bless the grave with the matching colour.
 * Repeat for all 3 colours.

Finishing up

 * Talk to the spirits until they block off the cave.
 * Quest complete!