I am Setsuna | Dark Samsara

Dark Samsara is the 'big boss' of I am Setsuna. To defeat him, you have two strategies: [1] Defeat his four parts first. Or, [2] Just finish him off!

I prefer you to do the #2 because if you're hunting for achievement, you can obtain a hidden achievement: Total Destruction trophy, by defeating Dark Samsara in his true form. It may be a little bit difficult since Dark Samsara can regenerate his HP every round (lesser HP regeneration if you kill all of his parts). But if you make a preparation, then it will be an easy task.

As my preparations, I equipped my characters with attack/defense boost, recover HP/MP when attack, and some other buff-functioned spritnites. This is the list of my characters for this battle, for your reference:

ENDIR
Support: Resonance, Physical Pride, All-Seeing Eye, Reginleif, Lifeforce Logic, Commanding Wave, Fatus, Megalith, Vinculum, Gratia. 
Command: Battlecry*, Aura. 
Talisman: Daemon Impact 

NIDR
Support: Commanding Wave, Physical Pride, All-Seeing Eye, Reginleif, Ultimate Truth, Guiding Power, Lifeforce Logic, Resonance, Megalith, Enigma, Destined Cycle. 
Command: Rebellion*. 
Talisman: Brave Will 

KIR
Support: Commanding Wave, Wise Testimony, Lifeforce Logic, All-Seeing Eye, Reginleif, Sigtyr, Fated Memory, Soul Rage, Megalith, Enigma, Destined Cycle. 
Command: Meltdown* 
Talisman: Sacred Heart 

* Battlecry + Rebellion + Meltdown = Armageddon.
This combo attack can give debuff effect to Dark Samsara, and buff the characters at the same time. The buffs/debuffs are affecting the attack, defense, speed, and evasion for both party and the boss.

With the debuff, after a few attacks you get from Dark Samsara, you can unleash the Rebellion with high damage.

After Dark Samsara is defeated (but not yet...), there will be a long conversation between the characters and you will learn the truth about a 'youth'. After you go into the light, you will be back into the past and you're landed in Nive Harbor. Exit the harbor and head to the village. You will be welcomed by Raishin. Later, he tells you about a youth he saw at Falling Snow Monument. Go there by walking through Dazzshire Woods.

You will meet Youth (obtain another hidden trophy: From Beyond Oblivion). Then, there will be a final battle, but too easy to handle. But first, make sure you listen to ALL of his lines, or you will not get the final hidden trophy: The Light at the End. He uses Inner Darkness attack that only give you scratches. After you listen to him, finish him off. It will only take 1-hit kill.

And now, make your own finale and enjoy the ending!

I am Setsuna | Kir's Legendary Spritnite: Doom

Go to Hiddbury with Kir in your party and go to speak with Hydor in his tent. A conversation will occur, he will tell you that there are some new travelers have arrived there. Head to Spritnite Pillar at the north of the village to meet them.

There, another conversation will occur and you will learn that they are Rare Bloods. And Kir's brother, Tor, helped them set free from the humans who tortured them. This conversation is quite long. Then, head back to the village to meet Hydor and the two of the sisters again. You have to find Tronne and have to go back to Spritnite Pillar. Make sure you save your game first!

Unfortunately, the news that Tronne went missing is not true. The sisters then attack you for the sake of revenge.

Syg is the healer, she can revive and cure other sisters. So target her first. Tronne is more to magical attack and her resistant is quite high, also immune to most magic. Quotra is good in melee attack but weak against magic, if you have any strong magic or combo that can deal high damage, go for it.

After they are defeated, they will vanish in a thin air and you will obtain Doom spritnite. Also, you will get Darkmoon, a new weapon for Endir, that has shadow-elemental attack.

I am Setsuna | Fides' Legendary Spritnite: Dragnarok

Have Fides in your party and head to Gatherington. Enter the cafe and talk to the man in the hood. He will tell you about a stolen spritnite. Then, leave the cafe and another cutscene will occur. After it's done, exit the village on the north side and head to the Fridged Caves.

Remember the area where you fought the last boss? Walk to there. Make sure to use the Save point and head to the center of the area. You will find the monster boy. Later, a dragon appears and you have to fight it.

The dragon is called Dysphormic Monster. It's quite tough. For preparation, make sure you have a character that can do AoE healing (Endir's Aura or Setsuna's Cure II) and equip some spritnites that can boost your defense/attack, and if you have Purikka Cobbler Salad, eat it. It helps you to boost your max HP. Make sure to stock up your Hi-Potion and Athenian Water, just in case.

Be careful whenever its HP reaching low, it will starting to attack you using Dragnarok that can hit all of your party around 150-200 HP.

After the dragon is defeated and the conversation has ended, you will obtain Dragnarok spritnite.

I am Setsuna | Julienne's Legendary Spritnite: Eclipse

Go to Royburg with Julienne in your party. In the center of the city is Cornelius, speak to him. After a long conversation, head to the Last Lands. Go to the middle of the town and turn right until you walk in front of the second house. Approach the door and you will get the new info about the blacksmith.

Then, head to Archimell Ruins on the lower left of the main land. Enter the ruins and head to the second area. Head to the right, then west a bit and turn right to find another portal switch with a red light. The last time you came here, the switch is not responding. This time, it will respond when you call the blacksmith's name. Activate it and get ready for a boss battle with Grinche.

Grinche is a tough creature with slow ATB. You can fight him with two attackers and have another character who can do AoE healing. Be careful with his Stop magic, if your characters are affected by this magic, it's Game Over.

After Grinche is defeated, you will get Eclipse spritnite.

I am Setsuna | Nidr's Legendary Spritnite: Rebellion

With Nidr in your party, go to Purikka. Go to the house on the top right corner and talk to Freyja. She will tell you that Nidr's friend is waiting at the Forgotten Shore.

Before you enter there, make sure you make a save. You also have to make sure that you're in a good condition and Nidr is at level 40 and above. Make him equip Stone Shield, this is a must! Put Avenger, Reginleif, or Lifeforce Logic for extra precautions. If you have any other boost damage/defense support spritnite, equip them to him. Buy 30 Hi-Potions or more.

Forgotten Shore is beyond Serendale. Cross the abandon village, and head there. Your 'friend' is waiting at the south shore. Talk to him and later, Freyja will come and challenge you a fight.

Never let your HP below 300, or you'll be killed. Make a wise choice between healing and attacking.

After you defeat her, you will get Rebellion spritnite and a Master's Sword.

I am Setsuna | Aeterna's Legendary Spritnite: Gearadia

With Aeterna in your party, go to Tenderville and walk straight and head into the first house. Speak with the man and he will ask you to go to an island.

Find the Island of Misfits on the southeast corner of the map and you'll find a city called the Nameless Village.

Once you enter the city, head to the house on the left and speak to the old man. Leave the house to trigger another conversation. Then, go to the lookout tower and you will see a big sheep monster. After you're done, go back to the old man's house, have another conversation and leave him and try to leave the village. You will encounter with the monster, but there will be no battle. The monster dies later and then go back to the old man.

After that, head back to Tenderville and speak to the man in the first house again and you will get Gearadia spritnite.

I am Setsuna | Setsuna's Legendary Spritnite: Holy Light

Go to the Nive Village. Talk to her dad in his house. After you're done talking, go to Dazzshire Wood. Then, take a left turn to activate another cutscene. Nidr will open a new path to a secret area. Go to the north, and you'll get Holy Light spritnite after the conversation ends.

NOTE: There is a mini boss battle on the south in this secret area. If you're ready, feel free to have a battle!

I am Setsuna | Endir's Legendary Spritnite: Genesis

After Time Judge/Eutess is defeated, go into the 'black hole' on the right corner. Do NOT cross the bridge if you want to get all the legendary spritnite for everyone.

You can get Endir's legendary spritnite starting point at Nive Harbor. Talk to the the first person you encounter right after you enter the area. And he will give you a letter.

I am Setsuna - World Key Treasure Chest Hunting!

This is the locations of the locked treasure chests in the early game in I am Setsuna. You will get World Key item after defeating Rhydderch in the ruin in Magna Valley. 

With this key item, you can get items such as weapons, Orichalcums (to upgrade your weapons), Mega Elixirs, some Spritnites and talismans. 

Part 01 

Part 02