Round 3 to 4
There is a 5 foot high wall separating the dirt floor of the room the party is in, and the tiled floor where the gnolls are. The stairway leads up to this tiled floor. I don't think Octar would want to try to do a 5' veritical leap to engage the fiendish wolf slayers (which is DC=20). Instead, I think he can find room next to Tullius at the top of the stairs. I'll place him there, if you'll allow me that latitude...
Octar moves up next to Tullius and with a swift jab of his blade, brings down that opponent.
Round 4
Ehldannis begins pronouncing the familiar syllables to produce another fiendish ally.
Tullius, diplaying skill which would make any Roman Centurian proud, sends a halbert-armed gnoll staggering with a battle axe to the face, and finishes him off with a thrust of the short sword to the gut.
Not to be outdone, Octar steps forward towards the next gnoll, and slices off its head. (critical 23 pts dmg).
A gnoll archer sends another shaft at Ehldannis, which goes wide. At the head of the stairs, the remaining gnolls converge on the company. Two swing their halberts at Octar. Both strike the warrior's mail, cutting and bruising the tender flesh beneath (12 pts total). Another swings at Tullius, with less luck, missing badly. The fourth, emboldened by his earlier success, rushes at Brioc, attempting to push him down the stairs. Brioc, now an experience combatant, sees the rush coming, and slices into his opponent with his scimitar, hitting only barely, and only because of the inspiration of Clannigan (AoO for 5 pts dmg). Seemingly undeterred, the gnoll slams into the druid, knocking him back off his feet. Brioc tries to land on his feet on the stairs (balance check DC=15 and a partial action), but fails and tumbles down the stairs, in a prone position (taking 5 pts dmg). He rises to his feet again at the foot of the stairs.
Mendicus moves down to Ehldannis, in order to get a better shot with his crossbow, which he readies, but is unable to shoot yet.
As for Dhormium, your spiritual weapon is still active, and you can direct it at another target. I'll assume you take a move action to use it to attack the other archer-gnoll, then cast sound burst.
The glowing axe strikes a brutal blow to the last archer, showering the pillar with blood. Then, at the dwarf's whispered prayer, an explosive sound pierces the din of combat. Tullius' opponent seems stunned by this, and the rear gnoll also grips his ears and staggers.
Marcus can still act.