Updated section on blue magic and the questline. I actually ended up writing a synopsis of the 30-50 questline, but will put it here instead of the OP because I fear it would be too damn long. Fanfiction advisory is in effect. >.>;;
30 The Long Search
Description - Momodi's face brightens up upon seeing you, as if she'd just found someone to hoist a problem on to.
Momodi is at her wits' end, explaining that she's been dealing with someone that for intents and purposes is just a loiterer in the Quicksand. The loiterer seems to approach novice adventurers and tries to get them to escort her into the Sagoli, but as that area is beyond the capabilities of the novices, she's continued to hang around. Since she doesn't want her to continue wasting people's time, she wants you to see if you can either help this person out or convince her to look elsewhere for help.
You're introduced to the loiterer, who turns out to be a young woman named Relm. She explains that she's looking for a bodyguard to keep her safe during a trip to the Sagoli Desert. She mentions she was about to move on to the Canopy or the Wench (insert joke about having the feeling Momodi was ready to throw her out), and agrees to let you escort her through the Sagoli. She orders you to meet up with her at Forgotten Springs.
Upon arriving in Forgotten Springs, you get a cutscene where Relm is talking to the Nuhn, who mentions an old friend of his that passed by some time ago. It is here that you learn Relm is tracking down her grandfather, who vanished while on a journey to catalogue and study beast behavior. The Nuhn mentions a set of ruins to the south that Strago was heading towards on his last visit, and suggests you start your search there.
Upon reaching the ruins, you find some left-over items (that she recognizes as her grandfather's belongings) but little else. Among them, a strange stone that does not react to Relm, but reacts to you. Deeper in the ruins, you find a large stone mural with a symbol that matches the stone's. Some exposition is given here, as Relm explains the ruins are of Belah'dian origin. That's when you and Relm hear a voice echoing from the mural.
The voice asks the wielder of the stone (AKA you) to "sting" the mural. In exchange for this, it is willing to share with you the fate of the old magus (which Relm concludes is her grandfather). Desperate to know the fate of her grandfather, Relm asks you to wield the stone and use it on the mural, and gives you some items that were among the things left behind by her grandfather (royal blue-dyed velveteen cowl, a copper jeweled gauntlet and the Soul of the Blue Mage).
30 Turning Blue
Description - The jewels embedded into the mural glow ominously.
Note: When you equip the BLU crystal, you only have 5 abilities. Magic Missile, Efflux, Magus Fist, Lancet, and Magic Hammer.
After equipping the BLU crystal, you are prompted to use Lancet on the mural. Doing so triggers a cutscene where the chain/rope/tentacle linking you to the mural begins to glow, and you see energy moving from you to the mural. Several of the jewels inlaid into the mural also begin glowing. The voice echoes again, saying the seal is weakening as the first of the small jewels shatters. Each shattered jewel summons the shade of a monster that you must defeat. During this fight Relm will help you deal damage but focus on healing you.
First Wave: Phantom Beetle
Second Wave: Phantom Ochu, Phantom Pugil
Third Wave: Phantom Bee, Phantom Wolf, Phantom Vulture, Phantom Ziz
Upon defeating each enemy, you'll see that enemy be absorbed into your gauntlet and your ability bar will gain a new skill related to that enemy (ex: defeating the Phantom Bee will cause it to be absorbed by you and Final Sting will appear in your ability bar).
After defeating the three waves, the jewel at the very center of the mural will shatter, releasing an Archaeodaemon. This demon is the source of the voice, and before attacking you says that the great azure beast killed the old magus, but that you'll soon join him. Upon defeating it, you get a cutscene where you absorb the daemon.
Relm is shaken by how this turned out, and asks you to meet her back at Forgotten Springs. Upon meeting up with her, she tells you she'll look into the great azure beast the demon mentioned, and also tells you that the jewels on the mural were apparently used to seal this beast that killed her grandfather. She sends you away and asks that you tell no one about what you saw in the ruins, promising to call on you when she has something to work with.
Pose with the job stone. "You assimilate the essence of the Archaeodaemon, making its power yours. You learn Lifebreak."
35 Behavioral Basics
Description - Relm seems to be quite glad to see you, as if she has something for you.
Relm tells you she's ready to get back on the road, as Strago's journal mentions a monster he encountered in his youth. The journal refers to the beast as "Hidon", and mentions that her grandfather has been in the ruins before. Strago kept renewing the seal on the monster, and now that it's loose, she wants to prevent more lives being claimed.
She's also looked into the stone you found, but didn't find much on it other than very vague legends. She's not even sure what its role is in all this, as she never knew her grandfather was a magus or mage of any kind. All she knows is that the symbol inscribed on it seems to be linked to the Belah'dian beast mages.
She's heard of reports of something sending the coblyns in Western Thanalan into a frenzy, and wants you to come with her. Upon arriving, you see the miners near Copperbell Mines trying to keep safe from the mobs of coblyns in the area. In the background, you and Relm catch a glimpse of a great beast: Hidon. Before you can run to it, even more coblyns show up, forcing you to focus on protecting the miners.
Like the first quest's fight, this battle has Relm acting as your backup/healer. Upon succeeding, it is quite obvious Hidon got away. With no more leads to follow, she suggests you wait until she hears of another sighting.
Pose with the job stone. "You have discovered new power from within the Soul of the Blue Mage. You learn Burst Affinity."
40 For Posterity
Description - Relm looks pensive, but brightens up upon seeing you.
Relm tells you that she's just heard of a Hidon sighting from someone she knows in the Black Shroud. She has a plan and will discuss it with you in Quarrymill.
Upon arriving, Relm reveals she's set several traps and wants you to help in chasing Hidon down, leading it to the traps. Then it'd be a matter of putting down the beast.
This fight is basically a giant chase sequence. You follow Hidon (level ??), do battle with it for a bit, then follow it until you corner it again. After the fourth fight like this, Relm appears with some local hunters looking to trap it. At that point a Great Marlboro joins the fray, inflicting the hunters with Bad Breath, giving Hidon the chance to get away. With Relm out of action because of BB, you end up having to solo the Great Marlboro. You absorb the Marlboro upon killing it.
After the battle, Relm asks that you meet up with her at Forgotten Springs. Upon doing so, she tells you that she's surprised at how clever Hidon is. It's almost as if it can analyze the situation and maneuver around things a dumb animal would fall for. With nothing else to go on, she asks that you return once she's heard of another Hidon sighting.
Pose with the job stone. "You assimilate the essence of the Great Marlboro, making its power yours. You learn Bad Breath."
45 A Blue Clue
Description - Relm looks as if she's seen a ghost.
Relm starts off by mentioning she's received a missive containing one sentence: Seek me out. What's disturbing is that the handwriting is her grandfather's. But Strago is dead, so that's impossible. Changing the subject, she mentions another Hidon sighting in Central Shroud. And again she has another plan to try to corner the beast and asks that you meet her at Bentbranch Meadows.
Once you arrive, Relm tells you that she's heard of a monster that's been seen wandering the Tamtara Deepcroft. Upon arriving you also run into members of the Lambs of Dalamud, who seem to be rushing to battle something. Further in you run into three cultists that summon a Piscodaemon, and when they see you and Relm, decide to attack you (the cultists do mention you're not the intruder they're looking for). Upon killing the daemon, you absorb it.
After the fight, you get a cutscene where cultists are trying to fight Hidon. As you approach, Hidon uses its absorb ability, instantly killing the cultists before running away. Relm is mortified because the beast is using an ability she's seen you use to absorb monsters, but is using it on people. She begins suspecting something else happened to her grandfather. Before you leave, you find another small note, this time saying "End this where it began". Again, in Strago's handwriting. Relm sends you away, saying she wants to fully prepare before facing Hidon, and will call for you when she's ready to put an end to this.
Pose with the job stone. "You assimilate the essence of the Piscodaemon, making its power yours. You learn Mind Blast."
50 Hidon Seek
Description - Relm's expression hardens as she sees you approaching.
Relm tells you she's made her preparations, but is beginning to feel unsure. Having seen Hidon absorb those cultists has given her an idea of how powerful the beast is, and understands such a power makes it extremely dangerous. She almost says more, but decides to just go forward and meet you at the ruins to the south of Forgotten Springs.
Entering the ruins, you find another note on the floor. This one says "The End". At the mural itself, you see Hidon. Before you can make a move, Relm tries to call out to the beast, trying to see if her theory of it absorbing her grandfather has any merit. She's convinced the notes were a way Strago could manifest himself from inside the beast to communicate. Hidon makes no response, and so the fight begins.
The Hidon fight involves the beast using lesser Blue Magic (all the spells you have obtained) along with an ability called Draw Out that inflicts Weakness on you or Relm when used. It has a rush attack that can stun you or Relm and will usually follow it with Draw Out. You can recover from Draw Out by using Lancet on Hidon. It'll also use the ability Grand Delta, which deals high damage. Relm will set up a barrier (like the books from the ACN lv30 fight) to protect you from it.
Upon defeating it, you motion for Relm to stay back so you can finish Hidon. The beast begins talking, but proves that Relm was wrong. Strago's essence only influenced some of Hidon's actions, but Hidon being a mere beast could not grasp all of the things it got from Strago, and wandered around confused and in pain (think of a certain little girl from the first episode of Full Metal Alchemist). Nodding to each other, you raise your gauntlet and absorb Hidon.
Back in Forgotten Springs, Relm thanks you for bringing closure to this. She finds it a relief that her grandfather was not trapped inside the beast as she suspected, and wonders if other horrors like Hidon exist out in the world. She tells you she'll stay in Forgotten Springs for a while, to wrap up things and digest everything she's seen on this journey. She does tell you to be careful, as this power you two have found seems to be dangerous in the wrong hands.
Pose with the job stone. "You assimilate the essence of Hidon, making its power yours. You learn Grand Delta."
...yes, once an idea takes hold, it never lets go.