They are a different race and class, and you've never met them before. They're headed straight for a very difficult dungeon, and you're not doing anything particularly important. This guardian also has a microphone and speaks your language.
What do you do?
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If they head in without waiting, I won't think anything of it and move along. If they appear to be waiting at the entrance, I'll make myself visible and grant them the opportunity to ask for help. Maybe I'll wave and say hi, too, just to show that I'm in a state of leisure at that moment and have the time to make friendly gestures at strangers.