I'll leave the rest to Caroline.
We were originally planning on keeping Seren’s outfit from arc 1, and just updating her belt, daggers, and arm armour. But as everyone else’s designs started coming together, we realized she just wasn’t as interesting in comparison and I really wanted to continue the trend of changing her look to line up with changes to her self-identity. Her new outfit is an upgrade focusing on hilighting her strengths: stealth, speed, and connections. We also decided to visibly link her to the Dorae-Kos by creating an emblem for them that’s kinda hard to miss on her back.