"Come here, Eros. I've got another job for you."
Karin knew that the little blonde had no idea that she was just the group punching bag. She could also heal herself, so no worries if a trap was sprung. Too bad Gnoryc caught onto the fact that a door is a trap. It was fun while it lasted.
Taking out the key Karin pointed to the part of the key that goes into the lock and said as if she were talking to a small child,
"You see this part here? Put this end into this hole. You twist it this way until the door is able to be opened. Then you can open it and look inside very first."
Hopefully the little blonde understood what she was told. Karin didn't want to have to explain this more than once and she wasn't quite sure if she could explain it in a simpler way. It wasn't easy being smarter than the rest of the party combined.