So I decided to root my phone, thinking it was a great idea and having no forethought for the repercussions if it went wrong. I have an AT&T Galaxy S4, model i337. It was on version 4.4.4, and I managed to root it using this method. So everything went fine with the root (no custom recovery). I got superuser to work, and I backed up my phone through Kies. I wanted to install a custom recovery to flash ROMs, so I used this. Big mistake. After I ran the program to install TWRP, my phone shut down. When I turned it back on, it booted into download mode immediately and displayed in the top-left under ODIN MODE: Failed to boot. Unfortunately, I had no access to the recovery menu. In addition, I could not turn off the phone short of taking out the battery, as it would repeatedly boot. I decided to look up ways to fix it on my own, some of which involved re-partitioning it and flashing stock. However, any attempt I make through Odin fails. Furthermore, Kies does not recognize my phone, and trying to fix it through a firmware update just gives an error message near the end. Somehow, I managed to make it boot to an error screen: Firmware upgrade encountered an issue. Please select recovery mode in Kies & try again. To my frustration, however, Kies still fails to recognize my phone. So, in conclusion, I seem to have screwed up my phone. I can still get into download mode, but anything I run through Odin just gives me the FAIL message. What should I do?