Naruto was filled with attacks that surpassed the imaginations of the fandom, bringing into focus attacks that were not only overpowered but also innovative. However, some attacks couldn't get the focus they deserved because the manga/anime was supposed to end. One of these attacks, a wide-range move, was the Truth-Seeking Balls.
These chakra masses appear on someone for numerous reasons, but they have the power to eradicate an entire village. Their power was teased through their usage in the fights of Madara and Obito. However, during the final fight between the protagonists, the protagonist fails to utilize them, hinting that these chakra masses might be Masashi Kishimoto's biggest headache during writing.
Disclaimer: This article expresses the opinion of the author.
Naruto: Why the Truth-Seeking Ball might be the most under-utilized attack

The Truth-Seeking Ball in Naruto is a black mass of chakra shaped like a ball. These chakra masses have a wide range of attack and are hardly the size of a tennis ball, but they hold disastrous power within them. These orbs appeared in shinobi, who could awaken the Sage of the Six Paths chakra, for instance, in Hagoromo and Hamura Otsutsuki.
However, these masses were also seen in users who attained the chakra of the Ten-tails by becoming its jinchuriki (Madara and Obito Uchiha) and also in users who were granted the Six Paths chakra from Hagoromo himself (Naruto Uzumaki). While the true potential of these masses wasn't showcased, one of the series' databooks revealed that a singular mass could destroy an entire forest.

However, their power, to some extent, was revealed through Madara and Obito Uchiha. The latter achieved them after becoming the Ten-tails' jinchuriki. Due to the malleable nature of the Truth-Seeking Ball, Obito often used these masses as a staff and shield to counter his opponents' attacks.
Similarly, Madara, who achieved these masses through a similar procedure, used them to counter overpowered opponents like Might Guy and even escaped death once with the help of the Truth-Seeking Ball. However, the only time these masses might have gained the spotlight was when they weren't utilized even a little.

During the Kaguya Otsutsuki Strikes Arc, when the protagonist had their final fight, Naruto could utilize these masses to his advantage against the overpowered Sasuke Uchiha. However, the protagonist only opted to utilize his main jutsu (Sage mode, Nine-Tails, and Six-Paths chakra), failing to use the Truth-Seeking Ball at all.
Moreover, these balls disappeared after the series concluded, meaning that their existence was 'worthy' of continuing into the future. This hinted that either Masashi Kishimoto only added them to the series for a visual effect or the author failed to utilize them because they became a headache. He had to leave them without developing any lore around them.
Final Thoughts
Just like Masashi Kishimoto, some fans might have overlooked these masses' presence after the series concluded. While it might be hard to pinpoint the reason why this attack wasn't given the spotlight, it should be safe to say that these black chakra balls were never a part of the main jutsu techniques.
Related Links
- Naruto: Why Obito pretended to be Madara Uchiha? Explained
- Naruto: Is Obito Uchiha the son of Madara Uchiha?
- Naruto: Why did Obito hate the Uchiha clan?