This setup is meant for difficult endgame content, such as Steel Path missions. If you are looking for something to use in normal missions and Sorties, check out my Speedgoth AoE Nuke build. This setup includes:

Sevagoth Build - Release The Kraken
Sevagoth's Shadow Build - The Kraken
Shadow Claws Build - Kraken's Klaws

The primary function of [Sevagoth] in this setup is to get into Shadow form as quickly as possible, giving us maximum uptime with the melee monster. Once the well is filled, we can jump into Shadow form and wreak havoc. We accomplish this with a Claw's build that boosts both status and crit, as well as attack speed. Giving the Claws Viral damage on top of the native I/P/S spread boosts the base damage via [Condition Overload], and allows [Healing Return] to keep the Shadow at max health so long as it's attacking something.