Key to Fallen Gate Quest in Everquest II

He will tell you to talk to Tundis N'oxyle in the Commonlands about joining the Thexians.

When you talk to Tundis N'oxyle he will ask you to kill 5 sand giants (right there beside you) to prove your worth to the Thexians.
When you kill them, go back to Tundis N'oxyle.
He will then tell you that they are having a meeting to officially join you to their ranks
So, head next back to Kanos X'aphon to receive your key
Oh, Tundis N'oxyle is located VERY west in commons from West freeport at the entrance to the Fallen Gate zone. His exact location is:

X:1,487
Z:-38
Y:-391

The easiest way to reach him is to head due west. You will eventually see the Griffon Tower. Follow the wall just a tad and you will see the Torchured Souls Tower. Keep following the wall and you will enter a maze of passages with sand giants in them. Just say on the rightmost pathway. You will reach the Entrance to FG.

To continue, when you talk to Kanos X'aphon again, he will tell you that to get the key you must kill the current Thexian leader for his key

If you talk to Kanos X'aphon again, he will teleport you to the meeting house. It is a really BAD place. You will be surrounded by 4 mobs instantly

Final Notes

The house is full of 3+ mob encounters

You get ganked when you zone. Atlest one is a healer, so target him first if you can. They are all named the same, so it is hard to tell the healer apart from the rest

The named you want is at the top of the house. 3 flights of stairs, and 4 sets of mobs. You can rest between fights, so dont worry about blasting away

At the top of the stairs, it is a little bugged in that sometimes a mob will get stuck in a wall. Be sure to use assist on the person getting killed and you cant fight back until you do

Kill the named. She will drop a ring. I cant remeber her name exactly, but it was Iana something. She drops a nice ring too

On your way out of the house, talk to the NPC again and he will give you a cap for your reward and some coin

Thats it. You now have access to the Fallen Gate Epic zone