The "xs" include is just a bunch of stocks that can help you with vector math stuff, they're not required for anything but they ease the job when dealing with vectors.
To remove knockback, I belive you could hook pre and post of damage and record victim's velocity in pre and set it in post so it remains unaffected... but I belive there could be a more efficient way by using a offset (if it exists, I don't know) or by using Orpheu module (which I know nothing about), so basically, other people should reply

I just wanted to make the "xs" include clear
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