sir tyranus wants me to help him fight but says i cant come back or something

what the hell does he mean i cant come back to ashleron or w/e its called?

*****SPOILER ALERT*****
The following text may tell you something that has been common knowledge on this forum for months. If you don't want to know. Don't read it.

Going through the Academy signals the end of newbie-land.
Ascalon gets burned to the ground and the rest of the game take splace in a dark, desolated, post-apocalyptic world. You can't come back to the nice, green, pretty Ascalon you're used to.

BAHHH spoiler alert! Do not read above post! It has prolly ruined it for me...

yeah um so when do i accept his quest?

Once you've done everything you want to do in the small world of pre-searing ascalon, talk to Tydus and go through the academy- you'll get to the main world(about 50x or more the size of what's available before entering the academy), and have the main portion of the game ahead of you. Basically, I'll do all the quests I can find, explore areas, and make sure to get all of the free skills I can before entering the academy- but once you've got your skills and you've explored the area, you might as well move on and get to the real game .