Résumé: WildC.A.T.S issue #0 basically tells how, when, and where everything started before issue one of the ongoing series. It acts more or less as the prolouge to the ongoing series. Issue #0 introduces you to the characters of the book without digging to deep into the backstory of every character. The characters being introduced to you in these pages are Jacob Marlowe, Void, Spartan, Maul, Warblad, Grifter, and Sister Zealot along with villains such as The Gnome and the Tirad. Void is really the only charcter that has a short origin story of how she became Void and who she was before she became the being she is now.
The issue does give you a plot set up for issue one as the Cats must find a "Gifted One" to aid them in finding this powerful Orb. If the Orb falls into the Damonites hands, the main threat to world and the Cats that are mentioned but not formally introduced. As you read on you discover that Grifter and Zealot are also looking for the gifted one on their own as they have not yet met, let alone have joined, the Cats. As the issue ends you see who exactly this "Gifted One" one is everyone is all in a hurry to find.
This all leads up to issue #1 of the ongoing and does a pretty good job of doing it.