This is the one you’ve been waiting for, right? What’s Weaver gonna use for his thousandth “Writing Glitch” post? ‘Cause, y’know, sometimes he deliberately chooses one for its ‘thematic elements’ or something, because of the date or post number or whatever… And you’re right; I did, even if the ‘thematic element’ isn’t obvious.
Change Your to You are.
Add a comma after human.
Either add a dash after threatening or change the comma after threatening to a period.
Change thats to that is and add a comma after.
Bouncer doesn’t quite fit the situation. Consider changing it to guard or guardian.
You’re a guardian at the gate between universes. For a human, you don’t look all that threatening — that is, until you show them your true form!
Or perhaps this:
You’re a guardian at the gate between universes. For a human, you don’t look threatening… until you show your true form!