domain Shellz.com

Shells - 5 figure territory

Shellz - High hundreds / low thousands

Collectable, craft or decorative shells are big business online. I'm not a fan of adding "z" to replace the "s" in domains, personally. However, I believe you may fetch something

From what I can see SHELLZ is copyrighted:
https://tmsearch.uspto.gov/bin/showfield?f=doc&state=4803:lery31.2.2
Not sure to what degree you are vulnerable, but double ''ll'' and then ''z'' also doesn't seem like a good option.
Maybe check brandable platforms.

shellz is so 1999 - 2008 for irc services