BOZ
Creature Cataloguer
and, got a response to that - turning it into a Plant (Shapechanger) and switching that spell out to regular invisibility.
see above post for comments.
posting what i have for this critter now:
Large Plant (Shapechanger)
Hit Dice: 4d8+12 (30 hp)
Initiative: +7
Speed: 30 ft. (6 squares)
AC: 23 (-1 size, +3 Dex, +11 natural); AC 24 as Medium-size humanoid
Base Attack/Grapple: +4/+13
Attacks: 2 slams +7 melee, or rapier +9 melee as humanoid (Medium-size; +8 melee Large)
Damage: Slam ld8+5; rapier ld6+5
Space/Reach: 10 ft./10 ft. (5 ft. as Medium-size humanoid)
Special Attacks: Sap, spell-like abilities
Special Qualities: Alternate form, darkvision 60 ft., plant traits, vulnerability to fire
Saves: Fort +7, Ref +7, Will +6
Abilities: Str 21, Dex 17, Con 17, Int 13, Wis 15, Cha 15
Skills: Bluff +7*, Hide +7*, Knowledge (local) +5, Listen +7, Spot +7
Feats: Improved Initiative, Weapon Focus (rapier)
Environment: Any forest or woods
Organization: Solitary or crew (2-4)
Challenge Rating: 3
Treasure: 50% coins; double goods; no items
Alignment: Always chaotic good
Advancement: 5-8 HD (Large), 9-12 HD (Huge)
Level Adjustment: —
PLANTs are always male and appear similar to treants but may likely be related to dryads, as well. While some sages think the PLANT is a treant/dryad hybrid, most scholars believe powerful magic likely spawned the race. While treants perceive themselves as "guardians of the trees," PLANTs view themselves as the dashing swashbucklers of the forests and woods. Although not as stodgy and condescending as treants, PLANTs share their hatred of evil beings and civilization's wanton destruction of the forest.
In their natural state, PLANTs stand approximately 15 feet tall and appear as slender, young pine, aspen, ash, or even olive trees. Their coarse bark ranges in color from blackish-brown to light shades of gray, while their needles or leaves, depending on the tree's species, vary from deep green to grayish-green. Bright trinkets of silver, glass, and other light-catching materials adorn their branches. Their love of these baubles accounts for the PLANT's name.
PLANTs speak Common, Sylvan, and Treant.
Combat
Haughty and brash, PLANTs do not patiently observe opponents or seek diplomatic solutions; instead, they rashly emerge from the forest and audaciously challenge foes. Extremely whimsical and prone to mood swings, bored PLANTs often assume humanoid form to pursue mischief or beautiful maidens. Despite their eccentric personalities, PLANTs immediately attack fire- wielding creatures without provocation.
Sap (Ex): The extremely sticky sap of a PLANT makes it dangerous to attack one with a piercing or slashing weapon. Any attack with a piercing or slashing melee weapon provokes an attack of opportunity from the PLANT. If it uses that attack for a disarm attempt, the PLANT does not provoke an attack of opportunity.
Spell-Like Abilities: At will—speak with plants; 1/day—charm person (DC 13), invisibility. Caster level 4th. The save DCs are Charisma-based.
Alternate Form (Su): A PLANT can assume other forms at will as a standard action. This ability functions as a polymorph spell cast on itself (caster level 4th), except that a PLANT does not regain hit points for changing form, and any individual quasit can assume only Large or Medium humanoid forms. When in humanoid form, a PLANT wears a courtier's outfit, and the PLANT's hair retains the color of its needles or leaves. (A PLANT in humanoid form loses its sap ability (and its vulnerability to fire?).)
Skills: *A PLANTs has a +2 racial bonus on Bluff checks used to seduce other creatures. A PLANT also benefits from a +16 racial bonus on Hide checks made in forested areas.

posting what i have for this critter now:
Large Plant (Shapechanger)
Hit Dice: 4d8+12 (30 hp)
Initiative: +7
Speed: 30 ft. (6 squares)
AC: 23 (-1 size, +3 Dex, +11 natural); AC 24 as Medium-size humanoid
Base Attack/Grapple: +4/+13
Attacks: 2 slams +7 melee, or rapier +9 melee as humanoid (Medium-size; +8 melee Large)
Damage: Slam ld8+5; rapier ld6+5
Space/Reach: 10 ft./10 ft. (5 ft. as Medium-size humanoid)
Special Attacks: Sap, spell-like abilities
Special Qualities: Alternate form, darkvision 60 ft., plant traits, vulnerability to fire
Saves: Fort +7, Ref +7, Will +6
Abilities: Str 21, Dex 17, Con 17, Int 13, Wis 15, Cha 15
Skills: Bluff +7*, Hide +7*, Knowledge (local) +5, Listen +7, Spot +7
Feats: Improved Initiative, Weapon Focus (rapier)
Environment: Any forest or woods
Organization: Solitary or crew (2-4)
Challenge Rating: 3
Treasure: 50% coins; double goods; no items
Alignment: Always chaotic good
Advancement: 5-8 HD (Large), 9-12 HD (Huge)
Level Adjustment: —
PLANTs are always male and appear similar to treants but may likely be related to dryads, as well. While some sages think the PLANT is a treant/dryad hybrid, most scholars believe powerful magic likely spawned the race. While treants perceive themselves as "guardians of the trees," PLANTs view themselves as the dashing swashbucklers of the forests and woods. Although not as stodgy and condescending as treants, PLANTs share their hatred of evil beings and civilization's wanton destruction of the forest.
In their natural state, PLANTs stand approximately 15 feet tall and appear as slender, young pine, aspen, ash, or even olive trees. Their coarse bark ranges in color from blackish-brown to light shades of gray, while their needles or leaves, depending on the tree's species, vary from deep green to grayish-green. Bright trinkets of silver, glass, and other light-catching materials adorn their branches. Their love of these baubles accounts for the PLANT's name.
PLANTs speak Common, Sylvan, and Treant.
Combat
Haughty and brash, PLANTs do not patiently observe opponents or seek diplomatic solutions; instead, they rashly emerge from the forest and audaciously challenge foes. Extremely whimsical and prone to mood swings, bored PLANTs often assume humanoid form to pursue mischief or beautiful maidens. Despite their eccentric personalities, PLANTs immediately attack fire- wielding creatures without provocation.
Sap (Ex): The extremely sticky sap of a PLANT makes it dangerous to attack one with a piercing or slashing weapon. Any attack with a piercing or slashing melee weapon provokes an attack of opportunity from the PLANT. If it uses that attack for a disarm attempt, the PLANT does not provoke an attack of opportunity.
Spell-Like Abilities: At will—speak with plants; 1/day—charm person (DC 13), invisibility. Caster level 4th. The save DCs are Charisma-based.
Alternate Form (Su): A PLANT can assume other forms at will as a standard action. This ability functions as a polymorph spell cast on itself (caster level 4th), except that a PLANT does not regain hit points for changing form, and any individual quasit can assume only Large or Medium humanoid forms. When in humanoid form, a PLANT wears a courtier's outfit, and the PLANT's hair retains the color of its needles or leaves. (A PLANT in humanoid form loses its sap ability (and its vulnerability to fire?).)
Skills: *A PLANTs has a +2 racial bonus on Bluff checks used to seduce other creatures. A PLANT also benefits from a +16 racial bonus on Hide checks made in forested areas.