There are two long side quest lines that you might want to do since if they give you quite important items.
1. The longest quest line is for obtaining the Ruddering/(Luder's ring?). This is a key item that allow you to fight enemy bosses you cannot see before. See those strange empty room in dungeons? There are most likely hidden bosses there. Best equipments in game (red and pink tiers) are from boss drops and genius blacksmith 2/3. Ruddering is also required for bonding quest of 2 out of 3 legendary lorimons, as well as obtaining the omega ( Ω ) stone.
- Quest 1: Demon research
- Talk to the old wizard on guild building's 2nd floor. He will ask you to collect 5 "Regarding Demons" books:
- Book 1: Divine Tree Village Mari's mansion
- Book 2: Reingernet city lord's mansion
- Book 3: Blood Moon Castle 2nd floor
- Book 4: Golden City Faris' mansion.
- Book 5: Gluck/Grack's cave B3F, required swimming 2
- Once you obtain 5 books, talk to the old wizard gain and complete the quest
- Quest 2: Research result
- A few day after you have finished the 1st quest, speak to the old wizard again to get the 2nd quest. This quest required you to best a boss in Maridis Ruins.
- Quest 3: Demon research 2
- A few day after you have finished the 2nd quest, speak to the old wizard and he will ask you to deliver the report to Along's house. HIs house is located at the middle north part of the map.
- Quest 4: Demon research 3
- A few day after you have finished the 3rd quest, speak to Along again to obtain the Ruddering.
2. The second longest questline is for obtaining treasure of resurrection. This is a key item that allow you to regain your magical girl power had you given birth to a human child. Warning: it is consumable and will disappear once you use it. The Japanese spoiler says that this item is required to get the TRUE END, but I haven't confirm this yet.
- Quest 1: Rescue the homeless man (Donoan) from a bandit in underground slum (south)
- Quest 2: The same homeless man will appear in Village of Whore / Succubus Village (southwest) and ask you for 500 Lo
- Quest 3: The same homeless man will appear in Divine Tree Village (northeast) and ask you for a healing potion.
- Quest 4: The same homeless man will appear again in Talirari Oasis and ask you for panacea potion
- Quest 5: The same homeless man will appear in the dungeon underneath the well near Dongu's Hideout. Beat the boss circling him. He will give you the treasure of resurrection (white gem).
Here's the full map for reference:
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