Here's a creature that I thought I'd share to show that even spellcasting shapeshifters can be converted to True20 with a little patience. Feedback is welcome--especially on the Change Shape ability (which is still pretty much right out of the SRD), since I intend to convert Freeport's Serpent People at some point.
[Notes: The stat block format in True20 omits level and advancement data. The aranea below is a 3rd-level creature, and advances by character role (usually adept) using the mixed-role rules (counting the creature levels as the original role). Night Vision is a free feat.]
Speed: 50 ft., climb 25 ft.
Abilities: Str +0, Dex +2, Con +2, Int +2, Wis +1, Cha +2
Skills: Climb 6 (+14), Concentration 6 (+7), Jump 6 (+8), Notice 6 (+9)
Feats: Improved Initiative, Iron Will, Night Vision, Power (x4)
Traits: Change shape, darkvision 60 ft., poison, powers, web
Combat: Attack +5 (+2 Dex), Damage +2 (bite, plus poison), Defense +5 (+2 Dex), Initiative +6
Saving Throws: Toughness +2, Fortitude +3, Reflex +5, Will +6
An aranea is an intelligent, shapechanging spider with sorcerous powers. In its natural form, an aranea resembles a big spider, with a humpbacked body a little bigger than a human torso. (The hump on its back houses its brain.) It has fanged mandibles like a normal spider. Two small arms, each about 2 feet long, lie below the mandibles. Each arm has a hand with four many-jointed fingers and a double-jointed thumb. An aranea weighs about 150 pounds.
Araneas speak Common and Sylvan.
An aranea avoids physical combat and uses its webs and spells when it can. In a battle, it tries to immobilize or distract the most aggressive opponents first. Araneas often subdue opponents for ransom.
Change Shape: An aranea’s natural form is that of a Medium monstrous spider. It can assume two other forms. The first is a unique Small or Medium humanoid; an aranea in its humanoid form always assumes the same appearance and traits. In humanoid form, an aranea cannot use its bite attack, webs, or poison.
The second form is a Medium spider–humanoid hybrid. In hybrid form, an aranea looks like a Medium humanoid at first glance, but a Difficulty 18 Notice check reveals the creature’s fangs and spinnerets. The aranea retains its bite attack, webs, and poison in this form, and can also wield weapons or wear armor. When in hybrid form, an aranea’s speed is 30 ft.
An aranea remains in one form until it chooses to assume a new one (which requires a standard action). A change in form cannot be dispelled, nor does an aranea revert to its natural form when killed.
Poison: Bite, Fortitude Difficulty 12, initial damage 2 Str, secondary damage 4 Str.
Powers: An aranea knows four supernatural powers, which it uses as a 3rd-level adept (using Charisma as its key ability). It prefers illusions and mind-affecting powers and avoids fire-based powers.
Typical Powers Known: Combat Sense +8, Heart Shaping (Difficulty 13), Light Shaping +8, Move Object +8.
Web: In spider or hybrid form (see below), an aranea can throw a web up to six times per day. This is similar to an attack with a net but has a maximum range of 50 feet, with a range increment of 10 feet, and is effective against targets of up to Large size. The web anchors the target in place, allowing no movement.
An entangled creature can escape with a Difficulty 12 Escape Artist check or burst the web with a Difficulty 16 Strength check. The check Difficulties are Constitution-based, and the Strength check Difficulty includes a +4 bonus. The web has Toughness +1, and takes double damage from fire.
Skills: Araneas have a +2 bonus on Jump and Notice checks. They have a +8 bonus on Climb checks and can always choose to take 10 on Climb checks even if rushed or threatened.