User blog comment:Phantomlink959/V3C4 preview/@comment-4010415-20151126072441

There are four biomes present during the fight:


 * Forest


 * Geyser


 * Field


 * Urban/ruined city

Interestingly enough, it's the same exact setup as we saw in a piece of concept art they showed in Free Play #22.

The geyser biome has some light blue crystal clusters, most likely Dust. I believe that the particular type is steam, which Miles mentioned existed during Extra Life. It makes perfect sense for the geyser biome to have steam Dust in particular. It appears that Mercury makes great use of the steam Dust to assault Yatsu and Coco with balls of condensed steam. He seems to somehow be controlling the steam with his feet or boots, considering it swirls around him as he spins around.

It also seems that things will go the way I expected. Yatushashi attempts to protect Coco while she uses her gun, since her mobility is very limited while her weapon is in gun form. Yatsu even tried to hit Mercury when he landed on Coco's gun and kicked her in the face. Too bad Yatsu is too slow, what with how cumbersome is sword is. It hits hard, but it swings slow, and Merc was able to backflip over it.

The biomes are specifically chosen to be difficult for Coco and Yatsu and give Merc and Em the advantage, through their speed and mobility.