My Trillium Panther 612 KSU went out. There is a red light flikering on the side. Is this light suppose to be steady or is it okay if it's flickering that way? What else may be wrong if all the phones are completely dead? Please assist.

I am afraid that we tossed out our last Panther test cabinet over a year ago. Frankly I cannot remember exactly what the LED flickering means.
As for the phones being dead, the internal battery that holds the programming memory is surely long since dead, so if you lost power, all of your programming is gone. Unfortunately, if no one has replaced the battery, it also most likely means that battery acid leaked onto the circuit tracings under it and it is possible, even likely, that the system is not salvageable.
Do you have a a programming/install manual?
Have you tried powering it down for 10 minutes or so, then powering it back up?
If powering it down and then up does not bring it to life, it is probably time to replace the system completely with someone newer (best option) or to buy a refurbished KSU to replace it.
Those old beasts are certainly not worth repairing.

Here' from the Trillium Panther 612 manual Page D-5. Take a deep breath and:

1. Connect the KSU power cord to the surge
protector(It assumes you have one)at the AC
power outlet. The recessed STATUS indicator
goes ON --with a slight flicker--indicating
that the KSU is operative.
2. Set KSU switch 4 BATTERY to ON Use a paper
clip or small screw driver to set dip
switches. (This is the battery Paul144 talks
about.)
3. Set KSU switch 1 PROGRAM to ON
4. Push recessed RESET pushbutton once.
5. Set KSU switch 1 PROGRAM to OFF
6. Push recessed RESET button again. System is
set at the factory default settings.
7. At station 10 press the intercom key.

If all that hoo-hah doesn't make it come back to life--say good-bye and Press the INSTALLERS link for help in your area and/or the EQUIPMENT link at the top of this page for a newer system. Good Luck.