At the beginning of the fight you're going to want to drop two plants and wail on him. This would be easier with a straight attack build that could burst him down, but it is still plenty doable.
![secrets of grindea phaseman secrets of grindea phaseman](https://media.rawg.io/media/resize/1280/-/screenshots/d12/d12d19a4309b91defea62e209d3e524b.jpg)
Basically just repeat this pattern, getting attacks in when you can. When he phases to the right side you want to drop a charged plant in the center, and after he phases to the center you're going to want to drop a charged plant at the top.
![secrets of grindea phaseman secrets of grindea phaseman](https://i.ytimg.com/vi/aHjGA1B7jq0/hqdefault.jpg)
While he is on the left side wail on him with attacks. When he is top go to the left side and charge a plant right before he phases there. While you are farming Plasma Bracelets you should also get a Brawler Plate since it is a more common drop. They aren't necessary to beat the Flying Fortress bosses, but I'd recommend getting them eventually and now is a better time than ever. Here you can farm for Plasma Bracelets if you want. Put any extra talent points into Surgeon and Brutality (the crit talents). Any extra silver skill points should be spent on Summon Plant in preparation for the Flying Fortress bosses, though you can put a point into Frosty Friend if you want. Go grab a MATK Rod from the Blacksmith, also grab a Metal Shield if you didn't farm a Barrel Shield. Just like fighting Gigaslime with any other attack based build, your attacks won't do as much damage but you got Cloud to add to your damage. For talents take Fencer, if you max it take Burning Weapon. Use weapon of choice (I prefer Big Branch) and spec all your points into Cloud Strike.
SECRETS OF GRINDEA PHASEMAN HOW TO
In this guide I will describe what skills and talents to take where, what items to acquire, and how to deal with various bosses. Hopefully if Frosty Friend (and maybe Summon Plant) is ever reworked this build will be a strong summoner build, leveraging damage from summons and basic attacks. This is a build that is hard mode viable but pretty weak with the current state of Frosty Friend (which is pretty decent in arcade but weak in story).