Metal Forge unlocks: Man Eater, Laser Panther Paint Job.
Once you say you are ready to collect the Dry Ice from the mines, Drowned Ophelia will appear and you are treated to a cutscene that shows her transformation. Shortly after though, she has her stage up and ready, Eddie gives the order to get the stage up. Time for a battle with Drowned Ophelia again, this time with her in it. On the Brutal Difficulty, this can be a fairly challenging fight as well. It will also test your abilities to use your solos. The more you have at this point, the better. The Light of Dawn is remarkably helpful against the Brides as well, as it will null the rain’s slowing effect.
First, upgrade your stage, then while it is upgrading, set a few units into production as well. Take some of this time to set the Heavenly Light (or the Rally Flag) in front of the right hand stage-side Merch Booth. Ophelia’s forces will consistently attack on this side. It will not be too long before she and her forces advance and attack the first Fan Geyser you see on this side of the area. You should a good number of troops (at least 3-4 units) and the first stage upgrade. Send them at the Drowning Doom. I recommend watching your load, keeping good tabs on how your units are doing. Produce a unit or two more, for safety, then go for the next stage upgrade. From here, slowly press forward, advancing the Rally Flag (either through solos or carrying it) so your new units will head into the vicinity of the fray. The Drowning Doom will attack in larger numbers at first, but will slowly dwindle if you are attacking viciously. Just press forward until you see her stage.
Move the rally flag one more time to keep it readily available. Now, use battle cry and have your troops just assault. Keep a steady bit of production from your stage though, as there will still be things attacking you and units dying off. Just wail away on the stage. If you have the Bring it Home solo, now is the time to play it near the stage.
Once you bring down the stage, the battle is over and Eddie gets a new idea for a unit for Iron Heade. It is time to talk to Mangus and press on toward the Sea of Black Tears.