[4ed-Gamma World] Help with Solo Design

[ShaggyMarco]

I am running a 1-shot that will basically be Lord of the Rings in Gamma World.
The PCs are going to be fighting a giant willow in a grove of death.

Terrain and situation: Basically, the willow will be on a 3x3 island, surrounded by a 2-3 square wide pool of water, ringed by a 1-2 square bank of mud (easy athletics or immobilized trying to move out), surrounded by a field of Grab Grass and a couple of odd normal trees.

Here's what I have:

Whomping Willow        Level 3 Solo Controller
Huge terrestrial plant                 XP 600
HP 192 (Bloodied 96)                Initiative -1 
AC 17; Fortitude 16; Reflex 13; Will 16    Perception +3
Vulnerable 10 Fire
Saves +5
Action Points: 2
Speed --                    Blindsight (anyone in water or grab-grass)

Traits

Threatening Reach: The Whomping Willow can make opportunity attacks against all enemies within 2 squares of it.

Triggered Actions

Sapped! * Encounter
Trigger: The Whomping Willow is bloodied
Effect: Immediately recharge and use Sleeping Sap.

Standard Actions

m-basic WHOMP! * At-Will
Attack: Melee 5 (one creature); +8 vs. AC
Hit: 2d6+4 damage, and the target is knocked prone.

M Whirling Whomp * At-Will
Effect: The whomping willow makes 3 WHOMP! attacks against 3 different opponents.

Move Action
Come to Me • At-Will
Effect: Pull one prone creature in a square of grab grass 2.

Minor Action
Sleeping Sap (bio, poison, sleep) * Recharge (5, 6)
Attack: Close burst 3; Close burst 6 when bloodied (all creatures in burst); +7 vs. Fort
Hit: 1d8+4 poison damage and the target is slowed (save ends.) First failed save: the target is dazed and slowed (save ends) Second failed save: the target is unconscious. 

Str 20 (+6)    Dex 6 (-1)    Wis 14 (+3)
Con 15 (+4) Int 9 (+0)    Cha 13 (+2) 

[Kurald Galain]

The Whomping Willow is from Harry Potter, not LOTR.

That said, the encounter would be more interesting with a bunch of minions or other minor mooks around. And a devastating move for this willow is to use the triple-whomp three times against the same character, is that intentional? Finally, how hard are you going to make it to fight from the water, or to climb out from there? What exactly does it mean to be prone while swimming, anyway?

[ShaggyMarco]

I know...this solo is a hybrid of Old Man Willow and the Whomping Willow.

Of course my Bilbo NPC is Willy the Bag-man, the oldest man in Gamma Terra.

-My initial idea was that the grab grass would take the place of additional monsters, keeping things interesting. I might make a set of 4 willowling minions and lower the Solo to level 3.
-I will specify that Whirling Whomp attacks must be on separate targets. Good point.

-My ideas for the Shallow Pool: Difficult Terrain, Grant Combat Advantage in it. If, at the start of your turn, you are prone and in the water, you must make an Athletics check (easy...it's shallow) to catch your breath. If you succeed, you can act normally this round. If you fail, you are dazed until the beginning of your next turn. Getting out will require moving into the mud, which may immobilize you if you can't move through it. If you fall unconscious in the water (whether you are at 0 HP or not) you automatically fail a death save each round. If you "Die" you've been sucked into the Willow and are slowly beginning to be digested. Your friends (or Tom Bombadil) can cut you out later. If you are small and in the water, you are always counted as "prone."

Thanks for the feedback!