Soren casts his spell, and the scraggly trees and shrubs within the forest twist and misalign themselves in the ghastly shapes.  Huge black thorns, like sickle claws, sprout from every branch and limb.  The five undead within the confines of his spell stagger forward, the thorns clutching and stabbing at them as the move.  In addition to taking obvious damage, they are slowed considerably.  Burr doesn't get the opportunity to take a swing yet, as none of the zombies are able to close upon him.

One of the zombies in the thorns raises his sword arm and rubs the side of his head, as the ringing of a bell haunts and torments it.

The last zombie outside of the thorns is able to move freely, closing the distance much faster than its undead squadmates.  It pauses briefly as Zelfa's arrow thuds into its chest, but then it continues to shamble forward, mouth flexing in a chewing motion.

Round Two:

1. Soren
2. Burr
3. Zefla
4. Giles
5. Zombies

Burr stays where he is, waiting patiently.

( I assume the previous roll still stands.)

Soren grunts in surprise as the ghastly dark thorns and sickle-like spikes are far less natural and more macabre than what he was expecting.

Nevertheless, he calls out, "I think perhaps circle to our left to force all of them through the Spike Growth as they shamble after us?"

Suiting his actions to words, Soren trots NW-->N-->N-->N (attack) -->NW -->NW.  As he goes, he whips his arm forward and lashes out with more thorny vines extending towards the zombie furthest to the west, latching onto it and dragging it further west through the Spike Growth.

Thorn Whip to hit westernmost (closest) zombie (melee spell attack with 30' range):  24
Thorn Whip damage (1d6):  5 + 8 more from 10' Forced Movement west through Spike Growth (4d4):  13 total damage, all magical piercing

"Or maybe split them up?" Zefla states as she moves southwest about 15' to get in the cover of the trees.  Pulling back the string on her shortbow she looses an arrow at the same creature again, the one not in the spike growth.

Attack: 22 Damage: 7

She then uses her BA to attempt to hide, stealth  28

“Great idea Soren!”  Giles starts to jog after him, trying to keep the group of zombies moving through the field of damage.  He points at one of the more injured appearing zombies and a bell goes off again.  

Toll the dead to an injured zombie : 7 necrotic damage if they don’t make DC 13 wisdom save.  

Toll save:  4

Soren's spell ensnares one of the zombies and pulls it through the vines, ripping and tearing at its grey flesh.  Giles' spell seems ineffective, this time.

[Regarding diagonal movement on a square grid:  I require the first diagonal movement to cost 10' (ie over 1 square, up 1 square) but the second diagonal movement only costs 5'.  Then back to 10'... then 5'... etc.  When you grid it out, this allows for a movement field more closely resembling a circle than a square with 4 corners, and it prevents character and monsters from being able to cover far more ground when moving diagonally.  Its also why I prefer to use hexes, but I stole this map and it came premade with squares.  So for Soren's movement, I cannot get him as far as you requested.  I assumed the goal was to get a location where a zombie can't attack him this turn.  If this doesn't work, please advise.]

The zombies continue to trudge toward their prey.  The zombie pulled by Soren is wounded but now at the edge of the thorns.  Its steps out into the open and chases after...

[Throwing this note in to document that this is the moment where I realized the zombies, despite having a speed of only 20' and being in difficult terrain, can still take the dash action and try to pursue more effectively.  I now have to change the map I just updated, and I'll roll some more damage for those running through the thorns...]

... it chases after Soren, crashing through the thickets, arms outstretched.  It draws close but was not close enough to attack this turn.  Another of the zombies in the thorns turns west as well, pursuing the druid and cleric.  But just as it reaches the edge of Soren's magical thornpatch, the damage proves too great and the dark forces animating the corpse abandon it.  It collapses onto the forest floor, an oozing pile of now fully dead and rent flesh.

Two of the zombies charge Burr.  One is close enough to attack... but Burr was waiting for his opportunity.  As the zombie raises its rusted sword to attack, Burr buries his axe deep into its pustulant chest cavity.  The undead soldier staggers, dropping its blade and falling to the dirt.  The other charges forward but succumbs to the piercing thorns.

The two easternmost zombies are free of the thorns and first seemed poised to pursue Zefla... but have lost sight of the halfling.  Instead, the turn and lope toward Burr, reaching him but without enough time to attack this round.

[I added blue dots to denote the zombies with swords.  Red X = dead dead.]

Round Three:

1. Soren
2. Burr
3. Zefla
4. Giles
5. Zombies

Gauging the speed of the zombie pursuing him, Soren figures he can keep it occupied while his allies attack.

Seeing Burr's somewhat errant swing still connect and fell one of the shambling undead, the druid shouts to Giles:  "Stay at least thirty feet away, or even better fifty feet away, so it cannot reach you.  Attack with your crossbow not-Father.  They seem very easy to hit."

Soren himself disengages and moves 30' due south, aiming to force the zombie to dash again to reach him.

Burr grins and hauls out the maul to strike at the armed dead.

Attack: 24 Damage: 11

Seeing the zombies dash surprises Zefla, but she's glad for two things.  One, that Soren's spikes seem to have really thinned the numbers, and two that she has done a good job hiding.

Stepping out from behind the tree, she aims her shortbow at the closest zombie and fires away (w/adv due to unseen attacker)

Attack: 25 Damage: 10

sneak attack dam:  5

She then goes to attempt to hide again behind the tree (BA)

Stealth  11

Giles nods and pulls out his crossbow.  He moves 30 feet to the southwest, targeting the zombie that was attacking Soren.  “Got him!  Let’s keep on the move..”

Crossbow : 15 to hit, for 9 points of piercing damage.  

Burr strikes what seems to be a glancing blow with his maul, but the rotten bones of the zombie warrior snap upon impact and it falls to the dirt.

Zefla's arrow rips through the side of the nearby zombie's neck.  The head is nearly severed, lolling off to the side with its jaws snapping ineffectively, before it too collapses.

That leaves the zombie pursuing Soren and Giles.  Ravaged as it was by the thorns, the bolt to the chest delivered by Giles is more than enough to snuff it out once and for all.

It has only taken seconds, but your party has dispatched the squad of zombies, without so much as a scratch taken.  A few of the zombies still twitch or groan in the dirt, but none of them are getting up again.

[I suspect the PC's probably feel pretty good about the outcome (even if the experience was unpleasant).  For effective use of resources and strategy, everyone can have inspiration.]

Soren smiles tiredly at his companions, then stares back at the ghastly black area of Spike Growth, clearly not fully comfortable with what he sees.  He licks his lips uncertainly and waits several more moments before (assuming no more zombies or other enemies come) letting it go.

"Well hunted.  When I claimed 'the forest defends itself,' somehow I had something more... natural in mind.  I suppose it worked, yet Barovia truly corrupts everything, even primal magic.  Since we have come so far, shall we explore the village past the little bay, a few minutes further on?  After that, unless we find a clue suggesting otherwise, we could turn back.  Everyone has warned us how dangerous it is to stray off-road or be out after dark."

Part of him thinks burning the zombies' bodies might be wise to ensure they do not rise again, but Soren hastily smothers the thought with a shudder.  No fire.  No burning forests.  My nightmares were bad enough even before I met Morgantha.

(Thanks!)

"What...what the hell were those things?!"  Zefla slowly rejoins the others, looking at the puddles of the former creatures, finding it hard to stop staring at them.  "The village past the bay?  Sure..." she agrees but doesn't sound too committal.  More like in a trance as she stares at the creatures, unsure of what they have all gotten themselves into.

Burr grins, it is hard to feel bad about making that which is dead act like it should and lie down, " We did well here.....these corpses will trouble no travellers or foragers at least."

" Yes, lets check the village before heading back."

It is only another five minutes of walking before a small village comes into view before you.  Vallaki writ small, the village is a cluster of what looks like no more than a dozen structures behind a low wooden wall.  The wall looks like it could be bounded in a single, athletic leap, but perhaps it is enough to keep things like those zombies you encountered at bay.  A wooden gate stands closed before you.  From what you can see of the buildings, they are in grave disrepair.  Many of the rooftops are covered with bound collections of pine boughs rather than tiles or shingles and some of them sag, looking at risk of collapse.

The trail you are on turns at the village gate to head east, following the curving shore of the lake.  There is an ancient-looking fieldstone bridge crossing a small brook that flows down from the north into the lake.  Where the brook meets the lakeshore, there is a long dock with several small fishing boats and a barge built on top of old wine barrels.  Looking up the length of the brook, you see it and the land rising higher and higher to the north, disappearing into mist-shrouded mountains.  It looks like another path may continue north past the village, following the brook up into the heights.

As you draw closer to the gate, it swings open unexpectedly.  A cloud of mist pours out from beyond.  Through the mist comes a skeletal warhorse and rider, both clad in ruined chainmail.  The horse moves slowly, purposeful, as they emerge from within the village and move down the trail in your direction.  The skeletal rider doesn't hold the reins.  Instead, it a long lance in one arm, the banner that once hung from it now little more than a few wisps of rotted thread.  In the other hand, it holds up a rusted lantern that sheds no light.

((Does the rider seem to have noticed us?))

[Insight or Perception check from anyone interested in a closer look at this thing...]