Seawolf (CR 3)

Medium Magical Beast (Shapechanger)
Alignment: Always chaotic evil
Initiative: +3 (Dex); Senses: darkvision 60 ft., low-light vision, scent, Listen +6, and Spot +6

AC: 17 (+3 Dex, +4 natural), touch 13, flat-footed 14 in seawolf or hybrid form; or 20 (+3 Dex, +4 natural, +2 leather armor, +1 light shield), touch 13, flat-footed 17 in human form
Hit Dice: 4d10+8 (30 hp)
Fort +6, Ref +7, Will +5
Speed: 10 ft., swim 40 ft., or 30 ft., swim 20 ft. in hybrid form, or 30 ft. in humanoid form
Space: 5 ft./5 ft.
Base Attack +4; Grapple +6
Attack: Bite +7 melee in seawolf or hybrid form; or longsword +6 melee in human form
Full Attack: Bite +7 melee in seawolf form, or bite +7 melee and 2 claws +1 melee in hybrid form, or longsword +6 melee in human form
Damage: Seawolf form: Bite 1d6+3; Hybrid form: bite 1d6+2, claws 1d4+1; human form: longsword 1d8+2/19-20
Special Attacks/Actions: Curse
Abilities: Str 15, Dex 17, Con 14, Int 10, Wis 14, Cha 12
Special Qualities: Change shape, hold breath
Feats: Iron Will; Stealthy; Weapon Focus (bite)
Skills: Bluff +3, Disguise +3, Hide +5, Listen +6, Move Silently +5, Profession (sailor) +4, Spot +6, and Swim +10
Advancement: 5-12 HD (Medium)
Climate/Terrain: Temperate aquatic
Organization: Solitary, pair, or pack (5-11)
Treasure/Possessions: Standard

Source: Stormwrack

Curse (Su): Any human bitten by a seawolf must succeed on DC 13 Will save or fall prey to a unique curse. On the night of the next new moon, the character transforms into a seawolf. The character's ability scores, class levels (and racial HD, if any), racial traits, and other special abilities are replaced by those of a seawolf. He or she also becomes chaotic evil in alignment. The curse can be broken by a successful break enchantment or remove curse spell or effect, but the caster must succeed on a caster level check (DC 15) to successfully undo the curse (which restores the character's race to human). The save DC is Charisma-based.

Change Shape (Su): A seawolf's natural form is that of a wolf-headed seal, but it can assume two other forms: a human or a wolf-human hybrid. The human form is unique; a seawolf in human form always assumes the same appearance and traits, much as a lycanthrope would. In human form, a seawolf cannot use its bite attack, and it does not convey its curse. In hybrid form, a seawolf's swim speed is reduced to 20 feet, but it has a much faster land speed, and it gains two claw attacks (or can use its claws to wield weapons, if it prefers). This form otherwise resembles the seawolf form.

A seawolf remains in one form until it chooses to assume a new one. A change in form cannot be dispelled, nor does a seawolf revert to its natural form when killed. A true seeing spell, however, reveals its natural form if it is in human form.

Hold Breath (Ex): A seawolf can hold its breath for a number of rounds equal to 6 x its Constitution score before it risks drowning. For a typical seawolf, this is 84 rounds, or over 8 minutes.

Skills: A seawolf has a +8 racial bonus on any Swim check to perform a special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming provided it swims in a straight line.

Seawolves are cunning and sly. They use their human forms in order to set others at ease but prefer to fight in their seawolf or hybrid forms. A common seawolf trick is to insinuate one or two members of a pack into a ship's crew. The spies then steer the ship to the waiting pack, or murder the ship's watch in the middle of the night so that their fellows can clamber aboard unopposed.

Shapechanger Subtype

A shapechanger has the supernatural ability to assume one or more alternate forms. Many magical effects allow some kind of shape shifting, and not every creature that can change shapes has the shapechanger subtype.

Traits: A shapechanger possesses the following traits (unless otherwise noted in a creature's entry).