Round 1
Erf moves to the right and swings ineffectively at the pile of centipedes. Fenenn, not liking the flavor of raw centipede, bites hesitantly, but with Erf's help it is enough to end the life of another tiny monster. (ooc: Erf is now flanking, so Fenenn's 13 becomes a 15 and hits.)
"Blastit revoltin' wrigglers!" Gildrim snarls, moving into the doorway and slashing with the very tip of his sword, neatly lopping another centipede in two.
The five remaining centipedes split up, one attacking Fenenn and two each attacking Gildrim and Erf, each of whom receive a painful nip. (ooc: 1 damage each to Fenenn, Gildrim, and Erf. You each get an AoO, but only Fenenn's can prevent the damage... and the fort save DC 10 which you all must make.)
Ter-raen guards himself against the centipede menace.
Initiative
Erf, 11/12, fort save and AoO pending <== You're up
Fenenn, 9/13, 3 fort saves due in 8 rounds, AoO pending, with one more fort save and dmg if it misses
Gildrim, 8/9, fort save and AoO pending
5 tiny monstrous centipedes
Ter-raen 14/14, AC 22 until beginning of next turn