Near Zora's Domain are several stone slabs that tell the history of the Zora. One of them tells of a time that Prince Sidon fought a giant octorok:
Prince Sidon's Great Escape
There was once a giant Octorok in Hateno Bay, large as a mountain, which terrorized the village's fishers. Hearing of their distress, Prince Sidon went forth to personally eliminate the offending Octorok. But this Octorok was a tricky beast.
After the prince dodged one of the stones it spat, it inhaled him whole. Such had been the fate of many strong warriors who went to slay the Octorok. Not one had come back alive. Just as it seemed Prince Sidon would be counted among them, the giant Octorok twisted in pain. The tip of a silverscale spear pierced the Octorok's stomach from within, revealing itself as the source of the beast's agony.
Incredibly, Prince Sidon had fought his way out by stabbing his spear over and over into the monster's stomach. Unable to bear the pain, the Octorok coughed up the prince and scrambled to escape. Ever since, the fishers of Hateno Bay have passed down this heroic tale: The Prince Who Slew the Fell Octorok.
After I found this, I went to Hateno Bay, looking forward to fighting a giant Octorok. I have not been able to find any such monster, however.
Is this tale just purely for world-building lore? Most of the tablets are, but at least one gives you a real hint about an actual treasure, so this could be meant as a real hint as well. Has anyone seen this octorok?