Details: After defeating Kahuna Nanu in the Seafolk Village Restaurant, he will tell of Guzzlord, the fifth Ultra Beast, and its whereabouts in Resolution Cave. This cave is found off Poni Meadows on your way to The Battle Tree, a path that wasn't accessible to you earlier in the game on Poni Island. Guzzlord, a Dark/Dragon Type, can be found in the basement of Resolution Cave.
You only need to catch one Guzzlord, the same that will be at Level 70 and the knows the Moves of Thrash, Gastro Acid, Heavy Slam, and Wring Out. As like all the other Ultra Beasts, Guzzlord will have one of its Stats doubled as it enters Battle with you. It wil be its Attack Stat that will increase here, as well as after knocking out each of your Pokemon during battle due to its Beast Boost Ability.
Guzzlord is said to be the final Ultra Beast you need to capture, but the storyline doesn't end here...