(Soooo....what do you do?)

Assuming you continue on straight toward the enemy, from the shelter of the woods, you can see the stockade at the center of an enormous clearing where the brush and trees have been cut and burned away.  A couple of small teams of gnolls with carts are hurriedly digging holes and burying things in the open space.  They keep an nervous eye on the surrounding forest. The stockade itself is a 20-foot-high barricade of upright logs, their upper ends roughly sharpened. There is about 500 feet of cleared space between the forest edge and the stockade.

Del asks the sprites to relay to the tree defenders - if they can do whatever to sabotage the catapults Stay invisible as much as you can, cut ropes or tangle them, tip over pitchbuckets, put out fires or light them where they en't wanted. Reassure the tree, it will be worth the risk of fire. We can end this, and our friend can produce endless water when we win. Some of us will be right there, if you see a spot to attack take it.

Del proposes to the troop commanders Move south along the edge of the clearing to the dry riverbed. No sense being too sneaky, make them react to our movements and wonder whether it's a feint. Which it ain't. Attack up the riverbed as you can.

I assume those burials will be some kind of necromancy, new enemies to pop up on the plains, unless anyone knows more detail? Just expect attacks from each pit

I would like if Q took R and did the Dimension Door thing, but not sure how you need to manage the slots. E could stay with the knights or come in with the flyers (on his own boots), hopefully M with the flyers and Flitterbug with M - with Del we can summon 56 Giant owls - lets get 56 of the best +Elwin?+R&Q to the inside fast - catapults can't really fire up well - and do some inside damage so the main force can make it through the stockade

Mindartis let's the group plan, knowing that he'll be better as a weapon pointed than a commander.

(( Elwin will decide to stay with the knights, mainly because he has Oroman and doesn't want to leave him to his own devices on the battlefield. ))

"Just tell me exactly where we are teleporting to again." Quentin asks to make sure. 

Raven would be willing to get in there and start striking down some of these evil creatures...

As you discuss, the foot troops start moving along the edge of the forest, south, toward the dry riverbed, noisily.  A few minutes later, you get news from a sprite that inside, they are spreading the archers out more, and concentrating on the south wall. 

"Would be nice if we could lay down a few fireballs among those archers..."  Raven notes to her companions.  "Also would be nice to get where I can acutally do something..." She kicks a tree nearby.

https://imgur.com/iiSbzxc

((sorry for the stupid link, cannot make image work))

Lord Quentin and Sister Raven, I suggest appearing just north of the easternmost boss house (bearing 285 / 5 degrees north of west / the little T for teleport on the image). Wait until we flyers have attracted some attention so you are not there alone too long. It should be a good point for Sister Raven to do some of her sneaking and smiting. We will head for a point just south of the thornwall (bearing 180 / the little F for flyers). I will send a Sending from the air if there is a reason to change that.

Del will assemble the summoners, Lord Mindartis, and get Lady Welles and Captain Garalm to help getting the rest or the 56 we have owls for - these have to stay alive and do damage to make the assault work

(Okay, assuming you;re done planning, been quiet for a while.)

You have your summoned owls ready.

The foot soldiers charge up the empty river bed toward the stockade wall, into a rain of arrows! They have no idea what they will do when they get there, but at least the archers are distracted.

130 archers fire! 1363 hit!

Oops..just a moment...100+5+2 hit! For 386 damage.

58   1

16 soldiers are killed outright,  8 more wounded.

16 24 22 22 19 24

From inside the stockade you hear shouts as flames rise up: looks like the sprites inside are up to mischief.  Fierce flames rise at several points, high enough that you can see them over the wall.

(You are up.)

((sorry, I was trying not to be the only person giving direction, and let people agree or not - and also wanting to know - what forces are we going to have when we fly in there? - so I know what actions to take. I guess I will assume we have 54 9th level wizards and druids and tanks, plus me and M on the owls <laugh>))

((at the start of the charge infantry is 500 feet away - archer disadvantage; by the time they are normal range we should be inside making trouble))

The flyers should take off before the charge starts, to split the attention. We fly high and fast to make it hard for archers, and land as indicated if that still works.

Can any of my detachment provide some defense or barriers or counterattack from the air?

It should be 5 rounds(?) in the air, only the last couple within range of most actions. Should we be going round by round or skip to some point?

One of the first things Del will do, from 150 feet out, is cast Plant Growth on the mass of gnolls by the south gate - 100 feet radius in all directions creatures are slowed costing 4 feet of movement for every foot traveled - leaving a single-file path to the thorn wall. If I have scale correct that should just encompass the southernmost catapult but not our landing zone? If I am right about that also leaving 5 foot wide path from us to the catapult and the stockade

Once we land the owls should make flyby attacks on archers and artillery until the summoners can come up with something better to concentrate on (walls would be nice)

(( Elwin will charge alongside the other knights up from the south, to attack... the wall? Sorry, I'm kind of lost as to how this is supposed to work. I presume the bulk of the enemy forces are behind the walls, so we'll either have to climb it or try to breach the gate. Soooo..... ))

MOVE: Ride as far as possible, using Oroman's Dash as needed, from wherever he is in the field toward the barrier, trying to locate the southern gate (if there is one,) and ignoring any gnolls in the open area.
ACTION: (1st Possibility) If he's close enough, attack the gate by ramming it with his lance, twice.
 - Lance Attack #1: 27, Damage incl. crits: 12
 - Lance Attack #2: 25, Damage incl. crits: 16
   (2nd Possibility) If he's close enough but there's no southern gate, pull out 50' of rope.
   (3rd Possibility) If he can't get close enough in one action, do nothing further.

DEX Save to avoid the necrotic "mines?" - 18

As Sir Elwin mounts up to ride behind the infantry, the rest of the cavalry joins him.

One of the knights looks doubtfully after the foot soldiers. "Should we maybe have had them cut some battering rams?"

Suddenly there is a tremendous roaring from the north.  A huge wave of water crashes through the forest, smashing down the north wall.  Logs are floating on the flood...no, wait, those are treeants?  And Fools are surfing on the wave, on shields and slabs of deadwood.  The wave continues, smashing down the south gate and a good chunk of the wall, literally washing most of the archers and gnoll soldiers out of the stockade. The burning pitch barrels are smashed against the walls, and the fire spreads to the stockade wall and the catapults.

"Oh, never mind," says the knight, lowering his visor, "Perhaps, if the spellcasters deal with the hags, the rest of us can wipe up the rabble."

A company of owls wait, expectant allies already mounted on some of them...

Quentin nods and says, "You ready everyone. I think the hags are calling out name." Ready to go fight as he uses his new staff to cast Mage Armor on himself. 

Guess Auntie don't surf. But I guess that is a signal if there ever was one. Well done, King of Fools! Del leads whoever is on the owls to a clearing in the stockade - the plan was just south of the thornwall, but adjusting to whatever conditions the fool-flood created. Not gonna play "Ride of the Valkyries" on the way over, despite the surf motif, Del is more blackway than wagner two thousand off the meters - two thousand surroundin’ us - travel two thousand kilometers to hang out with us - what’s up, danger?

As you fly over the remains of the stockade, you see that only a handful of gnolls remain inside, trying bring one of the catapults back upright under the commands of one of the Fangs of Yeenoghu.  The other Fangs battle a small band of treeants and poorly-armed fools trying to protect the tree. The wave that destroyed the stockade also tore away the tree's protective thorn wall. The water is still ankle-deep, but is now reduced to an overflowing stream bed, rather than a devastating flood.

Three green hags and three night hags are knocking water out of their ears, wringing out their robes, and screaming at each other about whose fault this is.  You don;t see Raninon Greyelf anywhere.

Mindartis joins Del on the owls for now, keeping an eye on the hags.

Raven moves in silently and stealthily.

Stealth: 15

She keeps her eyes open for the assassin as she does so...

Perception: 28 (passive is 20)

Del will land his detachment between the tree and the hags, trying to get a position so that Raven will be behind the hags if we attract their attention. He'll direct the casters that can to use walls or whatever control spells to split the hags from each other, and have whatever owls are left (some might have to drop concentration?) to attack the group trying to right the catapult. Del keeps concentration on his owls, so drops a Shatter on the hag group :10 foot radius take 12 thunder damage, half on DC 17 CON save

How about I roll a percentile you can adjust for whatever number of owls get to attack (they are +3 to hit / 2d6+1 damage) 52

...gettin’ old, they doubted us ... makes it that more marvelous ...

“This seems like a lovely reunion to break up.” Quentin says as the approach the hags casting Fire Wall between the two of them setting the flames to scorch the night hags. 

Fire Wall DC 15 Dex ST for: 26 Fire Damage