Have you been wondering how to make full use of your characters that you never play on? Such as that Hero character you made for a skill training badge? Or maybe those Elf and Giant assistants that you only made for more space? If you have not completed the Generation quests on those characters (or your main character), perhaps there is a way for you to still benefit from them. This is the guide that will help you determine so.
Generation One:
You can farm firewood from the final battle with Glas Ghaibhleann. Detailed information can be found here. Having access to massive amounts of firewood is useful for training Carpentry and Magic Craft.
Generation Two:
You can mine Mythril Ore in Barri Dungeon when you reach the Mythril Mine quest. Mythril Ore is useful for training Fragmentation and Refining.
Generation Three:
Baol dungeon can be farmed for Fireball Page 8 from Nightmare Humanoids and Arrow Revolver 10 from Argus. I guess you can farm Giant Headless and Argus for Transformation Mastery, but I'd recommend running Saga Episode 2 for those.
Generation Seven:
The Mirror of Memory dungeon will allow you to farm Ice monsters (except for Ice Bison) for Transformation Mastery and Taming Wild Animals without a Snow Crystal. The pass from the quest is tradable and can be transferred via pet inventory.
Generation Eight:
You can use Crumena for training Meteor Strike. Unfortunately, if you are doing G8 on an alt, you not be able to bring your main unless they are on separate accounts.
Generation Eleven:
If you and a friend are feeling lucky, you can try running Partholon Stone for Peaca Normal Enchants. First you must enter with 2 people. The person that is doing G11 must disconnect once you enter the boss room. There will be 2 chests after defeating the boss, one of them will have an enchant, and the other one will have a potion. You will only be able to open one of them.
For Golvan:
You can farm Golvan's Delusion for various Theater Mission mobs. Notable drops include Red Upgrade Stone, Blue Upgrade Stone, Dragon Fang, and Earthquake Cylinder. Be sure you leave the mission without approaching Golvan at the last stage.
Generation Fifteen:
If your character is over level 1000, you can farm the final for Larva Cocoons.
Generation Sixteen
You can farm the final for Giant Fireflies and Ghasts for Transformation Mastery.
I was actually meaning to write this guide for a while, but during my procrastination, content updates have rendered many of the things obsolete (you used to be able to farm G13 for Life Drain Crystals and Forest Golem Crystals, and various dungeons for passes). Some of this data may no longer be accurate because of all the nerfs G17 brought, but I hope this helps someone.