Oh, shut up and help me remodel the Octo-Kraken page!
That was intense.Ceodore Harvey
It is a good idea to come with full HP and with the best equipment at the moment. The player should focus all their attacks on the tentacles first and later the Octo-Kraken. Use the Band ability, Cross Slash, to lower the boss's HP quickly. Use a Spider's Silk to cast Slow on him and Protect to improve your Defense. A Ice Shield and a Flame Mail would help to absorb the elemental damage from the tentacles' attacks.
A simple strategy is to use a Silver Hourglass, which will cast Stop on every enemy other than the Octo-Kraken itself. This leaves the boss vulnerable to all attacks, which ensures a quick victory.