Then. Romancing another NPC triggers *their* romance, just like Tav would, and not yours, so.. You miss out on the personalized content there, too. I tried playing as Gale for a bit, but couldn't find *any* Gale specific lines all the way into the Grove and rerolled. I had kind of figured you'd get another fun scene where he'd end up in the Portal and someone would pull him out, but.. No. Just the same stuff.
I was expecting that much of the interactions would be the same, but the thing is, in Karlach’s case, some interactions don’t work since she cannot be touched until the start of act 2. So, if there was no change whatsoever, in some instances logic itself would be broken. So there were a few changes, thankfully, but just at the start. Afterwards the story flowed as any custom tav, and that left a lot of “wait, but HOW?!” moments, which is why I was threw off the experience, I guess.
