The Black Wyrm of Brandonsford

Let’s say as the combat rounds begin Gann is just getting to the base of the ladder. So the door is still open, and it would require Gann’s whole turn to climb up and close it. Nessa’s also up there though, and it was her Gann called to.

I assume that's all he'll be able to do for now. He's hoping to contain whatever/whomever this is, which he knows will be difficult with them being invisible.

Rolling...

Oh dear, Sable should have gotten some better sleep.

Cairn is an unusual game, in that there are not usually any modifiers for saves, and because in situations like this where one person is trying to tackle another, it's the person most at risk who makes the save, per page 62 of the Player's Guide.

So here, it's the thief that has to save...

On a success, Gann with have gotten hold of whoever or whatever this is; failure will mean Gann crashes into some crates and deals 1 damage to himself. Your armor might protect you here, but were you wearing it all night? Perhaps not the helmet?

Need Willpower saves from both Gann and Sable, please. Not from Kit.

What exits are in the kitchen. I assume at least 2. One which goes outside and another which goes into another room. Anything else like a door or window?

I had said that Wren tried to get into the hatch before it closed... Did she make it? And is the consensus that the invisible thief is down in the cellar with them/us?

Rowan, I described the kitchen thusly before, so nope, no windows.
Regarding your action, Rowan, yeah, you can open the door and move into the kitchen. If you want, from there, you can turn and lock the door, or get right up to Nessa.

Wren -- nope, that's not an option because Nessa closed the door before you acted. We're just coming to the end of Round 1, which started when Gann yelled. Wren and Sable failed their DEX Saves and needed a moment to orient before they act starting in Round 2 -- which is right around the corner, after I resolve the results of the Willpower Saves from Sable (passed) and Gann (has yet to roll).

Gann didn’t wear armor while in the cellar due to space but he would have had the helmet while on watch. Does that mean no damage then? Funny he went head first!

Used a Die of Fate to see if the helmet protected you, Gann. Nope, please take 1 damage to your hit points.

New Round coming. Stand by!

Everyone is up and can act in whatever order you all want!

Downstairs: Gann is faced with a big-ass rat monster! Sable is across the room, but the space is small enough to reach wherever and still perform an action.

Upstairs: Nessa stands on the closed trap door. Rowan is in the room, and Wren is up and at 'em.

What do you all do?

Is it between me and my previous hiding space? I’m curious how possible it would be to go for my sword. And would swinging it in here be completely impractical?

Nope, your path back to your weapon is not blocked. It'll take your move and your action to get your sword, but you could also end up back in the thing's face if you want, ready to attack next turn.