(Escella should be on the other wall by the arrow slit. She was hoping to take potshots at the gnoll1 and gnoll3 from the prior encounter before the doors opened. That's why I posted attack rolls in message #3011.)
I put you near the window that Lionel peeked in early, to look out for trouble. It was the closest translation that I could make in my head to interpret your post, because there aren't any arrow-slits. If there were, the gnolls probably would have stayed inside to shoot at you. Out of curiosity, what are you seeing that looks like an arrow slit?
It's a window, just like the one I have you standing by, but on the north side. I will move her to the north one. She can certainly use it like an arrow-slit (though they are high on the wall and stained-glass). She will have to knock some glass out to get an arrow through (it's already cracked, but none of the holes provide a good firing-line. It would be better if she could get 5 ft. above ground-level, so she could fire downward. Lionel had to climb the wall to look through the south window from outside.) I will get back to you with a post of what she can see from that window ASAP.
She has sharpshooter and Energy Blast. The limitations of an arrow are not hers. And Gnoll1 and/or Gnoll3 were on the roof of the neighboring building. So looking "up" might helpful for targeting them.
Escella peered out the cracked stained glass of the northern window. From there, she could see the Phylund Lith and the roof of the building that was built into it. The two gnolls that had been up there were gone, presumably climbing back down by way of the trees to the east, which were out of sight.
She was about to turn away in disappointment, when the two archers that had been near the front doors came into view, running between the two buildings. She could only just make out the top of their heads as they ran, but that was more than enough for her skills.
Lionel walked up to the doorway and spotted the large gnoll coming down the staircase. He thought about how the gnoll moved down the stairs and thought he saw a good opening. He lifted the crossbow, aimed and let the bolt fly.
Next, Lionel moved up and ducked down behind the upturned table.
The doors burst open, and Oh-Six is off like a shot, dodging and weaving into the main hall and straight for the Large Gnoll on the stairs, whistling as it flies.
Tommi follows into the room, and sidesteps the large gnoll Pikeman before him. He tries to get a clean shot at the beast on the stairs, which is now distracted by the flashing, hovering Oh-Six. He lets fly the first of his three stones, which hits the creature in its throat.
He's pleased finally to be in the fight, and Gutter, it seems, pulses at his hip, as if yearning to join the fight.
Move: I think he can get to AC 37 with 60' movement. That's not enough for flyby, and so since I want him to be in range for Tommi, Oh-Six will HELP as his action (and it has Shield ready).
Move 30' and Bonus Dash to Y38 (I don't think he can get a clean shot with just a move).
Action: Magic Stone in sling, w/ Sneak attack and Advantage: 1d20+7=18 (hit). Damage = 4d6+4=20 magical bludgeoning.