To start of, Reach level 7. You should get a quest from someone named Yoff. Go to the Arena next to Filia and talk to Yoff. He should give you the keyword "Ancient Irinid".
Complete the quest and talk to Castanea using the keyword. Complete the quest.
Eventually you should get another quest. Talk to Yoff again, And he will give you an ancient medal. I would suggest to put it in your bank, or somewhere out of the way.
Soon you should get another quest. Yoff wants you to gain Castanea's trust, So go and talk to her. She will ask you to find the lost elf, so grab your L rod and find one. Bring the lost elf back to Castanea and complete the quest.
You should get a quest called Hagel's assignment. Go and talk to Hagel, and buy some sketch paper.
Longa desert ruins normal
Hagel will ask you to sketch the Ruin guardian. So, run down to Longa desert ruins dungeon and drop a random item.
By no means a hard dungeon, So you should be able to solo it. The rest rooms are annoying, Though. You should be able to kill the young emerald Beetles in 1-2 shots. The only threat are the young stone masks, who sometimes use firebolt. Sand mimics and young blue pythons should not cause to much trouble.
The ruin guardian starts of riding a horse, But you don't have to kill it. Run up and sketch the ruin guardian quickly. It's your choice whether to kill it or not.
Run back to Hagel and talk to him. What luck, he wants you to sketch another monster. The stone horse keeper to be exact. But this time, it's in Rano. Head towards Karu forest now.
Karu forest dungeon
I would suggest a party for this dungeon. I don't remember it at all ,so I can't really offer advice.(Yes, my memory is that bad)
Here is some help from Toric.
You can also get the sketch from the pot-belly spider version of the dungeon, apparently.
Return to Hagel and talk to him. Complete the quest and you have yourself the keyword "Book of the Irinids".
Quests of doom
First, Get the title "Rano explorer". To get it, travel to every landmark in Rano. If you're to lazy to find them yourself, here is a map.
Once you have said title, Equip it and travel to Quilla base camp. Talk to Alexina with the keyword "Book of the Irinids". She will give you a choice of 3 quests.
1: Investigation of Maize
The most popular, and arguably, easiest quest. It requires you to run Maize normal, and get the boss gargoyle's Boots, Hands, or Pauldron. Drop one of those items to enter a harder version of Maize. The boss will be 3 gargoyles with a shining version of what you dropped. Kill them and you have a chance of getting the shining part. Repeat until you have all 3 parts.
Then get level 16 exploration to make a statue from them. Don't complete the exploration quest, though, or you will lose your statue. Open up a party and recruit some people for your run. If you're evil, or poor, you can even charge money for a spot. Complete the dungeon and finish the quest.
Note that you only have to complete the run. You don't have to be the party leader, so if you're lazy you could just buy a spot.
Some advice from arklian:
Requires you to sketch Rano field bosses. in other words, sketch:
1. Giant Short Horned Gnu
2. Giant Long Horned Gnu
3. Gold-tailed Mongoose
4. Head Hyena
5. Wolf-striped Desert Spider
6. Gold Kiwi
7. Giant Gold Forest Mushroom Spider
8. Gold Forest Lizard
Not recommended. Kitae will explain why...
If, however, you choose this quest, Zachman111 wrote a guide on how to deal with this quest.
3: Sandworm hunting
Kill a Sandworm. You must kill it. Sounds easy, huh?
It would be, if not for the fact that Sandworms have 100,000 HP, spawn once every 24-48 hours, and everybody wants that finish. But who knows, maybe you will get lucky.
Well done if you made it, you have completed the hardest segment of the quest, depending on your luck. Hit the complete button. Now, who wants to sneak into the Giants village?
Speak to Alexina, and she will tell you to sneak into Vales and talk to Taunes. Make your way to Vales. As soon as you spot the first guard, use hide and run to the weapon shop. Speak to Taunes and mess around with some giants if you want. Escape by continent move or the Mana tunnel next to Vales. Complete the quest.
You will receive a quest from Castanea. Run along and talk to her. Uh oh, She's pretty angry at you. Watch your cut scene and wake up in Quilla base camp.
Talk to Alexina and she will give you a collection book for 15 medals. If you remember, you already got one from Yoff. Grab that and put it in the book. 14 medals to go!
These ancient medal can be found inside the boundary's of Landmarks in Rano and Connus. I found most of mine at the monkey mark, but all the landmarks work. If you find a chest with a medal, Channel change quickly. There should be a chest close to where the other one was. A good idea is to alternate between Rano and Connus.
At the start, It will be very easy. The last 2-3 medals will be very hard though, depending on your luck. Since the medals are untradeable by any means, you're on your own. Once you have every medal, hit the complete button in the book.
Congratulations! You now have your transformation. Now you can have fun grinding levels to train the skills.