First of all you haven't bricked your Deneb by just using Luciferin

Second, you don't need to pull out Deneb if it doesn't boot. Putting the Jumper into ROM position, disables Deneb's flash so it won't interfere in the boot process.
Second, I'd suggest you to remove everything from Deneb's flash and boot your system.
Poseidon doesn't need to be in Flash except you require USB things before booting Workbench (like USB mouse, booting from USB sticks etc). If you don't need such stuff, there's no need to have Poseidon.library, classes and Deneb devices into the Flash.
So... If your system works just fine without anything... then install Poseidon, configure it and if it works, insert into Deneb's flash the correct device that works on your system, and the PsdStackLoader that resides on your Env-Archive folder. Don't forget that every change you make on the USB configuration needs a fresh PsdStackLoader!