The Unanswerable Problems

The Unanswerable Problems is the first act of Tighnari's Story Quest, the Vulpes Zerda Chapter. In order to unlock this quest line, the player needs a Story Key, must have completed the , and reached Adventure Rank 40.
During the Story Quest, the Traveler helps Tighnari investigate strange corruption emitting from the forest.
==List of Quests==
# The Start of Contamination
# Into the Hinterland
# Heart of the Machine
# Garden Memories
==Summary==
;The Start of Contamination
Walking around Sumeru City, the Traveler and Paimon meet up with Katheryne at the local Adventurers' Guild, who tells them that there's been a commission at Avidya Forest as the area has been "contaminated." The two initially suspect a new Withering Zone, but Katheryne denies this, stating that it appears to be something else. Since Tighnari would not turn an eye to any dangers to the forest's inhabitants, Paimon suggests visiting him first.
Arriving at Gandharva Ville, the two find Tighnari treating a boy named Yara before learning why they came to visit. To help improve Yara's condition, Tighnari suggests buying Vasanti Grass, although he also rules the possibility of having to get some himself. When he goes to buy some from Mahir however, he learns that the merchant is closed. Mahir explains that he and the other merchants pooled together to buy some mechanical parts, which were stolen by a crab-like machine that fled deep into the forest; the merchants could not pursue due to having heard rumors of the contaminated zone.
Talking to the other merchants, they confirm that the thief is indeed a mechanical crab that is solely interested in mechanical parts. After loading some spare parts on a Sumpter Beast and walking it along a path, the thief comes out to attack. After repelling the thief, the group is surprised to discover that it lacks comprehension regarding complex questions. The Traveler stays behind to watch the crab while Tighnari looks for the stolen items and recovers them. As more were missing, Tighnari tells the crab that he'll give him more parts if it brings them to its hideout, which it agrees to.
To ensure that the crab wouldn't escape, Tighnari places several traps before collecting the stolen goods and bringing them back to the merchants. With Collei's help, he makes a cure for Yara before asking the Traveler to accompany him back to the crab.
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;Into the Hinterland
The two return to the crab and are surprised to see that it made no attempt to escape while they were gone. Tighnari asks the crab to take them to its hideout, which it agrees to in return for more parts. On the way, they discover a glowing Sumeru Rose and Tighnari explains that the Sumeru Rose is also known as the "Ley Line Lodestar"; its unnatural brightness indicates that the Ley Lines in the area are dangerous.
As they continue walking, Paimon notes that they haven't seen any animals, which Tighnari believes is a result of the animals sensing the difference in the Ley Lines and having fled. He decides to test a Purification Device he made, which works and brings the animals back, although they drive them off to prevent them from damaging it. The crab suddenly darts away, where they find some Ruin Machines and defeat them, discovering Jasar, who had accidentally wandered into the area to pick herbs. He thanks the two for saving him but becomes terrified upon seeing the crab; Tighnari, noting that he had stayed too long in the contaminated area, sends him to Gandharva Ville for recovery.
After setting up camp, Tighnari and the Traveler take turns standing guard to ensure nothing would attack them as they slept. The Traveler rests first before waking up earlier than Tighnari expected, who explains why the Akademiya banned research on mechanical forms. The crab serves the two coffee, although Tighnari declines to go to sleep, leaving the Traveler on night watch. After he wakes up, they clean up the campsite and continue making their way to the source.
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;Heart of the Machine
Arriving at the source of the disruption, the group discovers that a massive group of Ruin Machines had made the place their home. After destroying them, they discover an extracting machine which Tighnari realizes is causing the contamination. The Traveler doesn't feel well, but insists on assisting Tighnari in shutting the machines down. As they wonder where the controls are, the crab runs off and they follow it.
The crab stops at a laboratory where they discover a person laying down. Paimon yells at him to shut the machine off, but Tighnari realizes that the man has been long dead and begins to investigate. He discovers some tape recordings and puts them in a projector, where they learn the crab's name — "Karkata," and the deceased researcher — Abattouy, who Tighnari knew during his time at the Akademiya.
Finding another tape, they discover that Abattouy was trying to make Karkata a truly living life form and had programmed it to try and make coffee. Running out of energy and Mora, however, he decided to create the Ley Line extractors as a power source. After discovering yet another tape, they learn that Abattouy gave Karkata "instincts" and had turned on the last of the extractors. However, having overcharged them, he succumbed to the Ley Line energy before he could shut the extractor down.
After finding the controls, they shut the extractor off before visiting Karkata again, where it tries to "repair" Abattouy to no avail before shutting down from overdue charging and maintenance. As they return to the extractor, Tighnari tells them to inform the Adventurers' Guild the situation has been resolved. As the Traveler asks on what would happen to the laboratory, Tighnari states that everything would need to be returned to the Akademiya under Akademiya protocols, and Karkata would likely be disassembled and put in storage. He tells them to meet him at Pardis Dhyai the following day.
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;Garden Memories
Returning to Sumeru City, the Traveler informs Katheryne that the situation was resolved, who rewards them for their efforts. Still worried about Karkata, Paimon suggests they visit Tighnari at the arranged spot and try to convince him to not turn Karkata over to the Akademiya.
At Pardis Dhyai, they find Tighnari, and much to their surprise, Karkata. Tighnari is upset by the disruption but he admits that he did not clarify himself yesterday; he did not follow Akademiya protocols since he was not one of their members and knew that they couldn't get their hands on Abattouy's research, so he only took a few with him and destroyed the rest and the laboratory after burying Abattouy. He repaired Karkata and brought it to Pardis Dhyai since it was a relatively secluded spot, but contemplates taking it on as a research assistant in the future.
==Characters==
==Soundtracks==
==Other Languages==
==Change History==
es:Preguntas sin respuesta
ja:答えのない課題
pt-br:Problemas Sem Solução