Yes, I prefer the standard grapple check to climb out (vs Climb checks), the silly elastic action to close the hole, etc.
Okay then, let's use that and get on with the stats.
I cut down the DR from a treant's 10/slashing to 5/slashing, since I don't think these things should be as tough as a walking oak tree.
It's all pretty straightforward now apart from the question of how much damage it does with its "whip". Do we treat it like an actual whip [1d4+7 nonlethal?], regular damage like a tendriculos's tendril [1d4+7?], or a no-damage grapple like the original [special?].
Pitcher Plant, Giant
Large Plant
Hit Dice: 5d8+20 (42 hp)
Initiative: -2
Speed: 0 ft. (0 squares)
Armor Class: 14 (-1 size, -2 Dex, +7 natural) touch 7, flat-footed 14
Base Attack/Grapple: +3/+12
Attack: Tendril +7 melee (1d4+5)
Full Attack: Tendril +7 melee (1d4+5)
Space/Reach: 10 ft./0 ft. (20 ft. with tendril)
Special Attacks: Drowning, improved grab, swallow whole
Special Qualities: Blind, damage reduction 5/slashing, tremorsense 20 ft., plant traits
Saves: Fort +8, Ref -1, Will +1
Abilities: Str 21, Dex 6, Con 18, Int -, Wis 11, Cha 3
Skills: —
Feats: Blind-Fight (B)
Environment:
Any?
Organization: Solitary or cluster (2–8)
Challenge Rating: x
Treasure:
10% coins?
Alignment: Always neutral
Advancement: 6-8 HD (Large); 9-15 HD (Huge) [
based on Tendriculos]
Level Adjustment: —
Combat
Blind: Giant pitcher plants are immune to gaze attacks, visual effects, illusions, and other attack forms that rely on sight.
Improved Grab (Ex): To use this ability, a giant pitcher plant must hit a creature at least one size smaller than itself with its tendril attack. It can then attempt to start a grapple as a free action without provoking an attack of opportunity. If it wins the grapple check, it establishes a hold and can try to swallow the opponent in the following round.
Swallow Whole/Drowning (Ex): A giant pitcher plant can try to swallow a grabbed opponent by making a successful grapple check. The interior of the plant is a vase filled with digestive fluids, each round the opponent takes 1d4 points of acid damage and must succeed on a DC15 Swim check or sink under the fluid and risk drowning. A swallowed creature can climb out of the vase with a successful grapple check. This returns it to the plant’s maw, where another successful grapple check is needed to get free. The inside of the vase is lined with needle-sharp spines that do 2d4 piercing damage to the opponent for every grapple attempt they make to escape. A swallowed creature can also cut its way out by using a light slashing or piercing weapon to deal 25 points of damage to the giant pitcher plant's interior (same AC and DR as the plant's exterior). Once the creature exits, elastic action closes the hole; another swallowed opponent must cut its own way out. A Large giant pitcher plant's interior can hold 2 Medium, 8Small , 32 Tiny, 128 Diminutive or 512 Fine opponents.