Whee, DM allowed the snake! Er, right, sparingly. (BBEG, be afraid, be very afraid)
Legendary Snake with the Flame-Element template:
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Large Elemental (Fire)
Hit Dice: 16d8+112 (184 hp)
Initiative: +7 (+7 Dex)
Speed: 30 ft., climb 30 ft., swim 30 ft.
AC: 22 (+7 Dex, -1 size, +6 natural)
Attacks: Bite +19 melee
Damage: Bite 1d8+12 and +2d6 Fire and poison
Face/Reach: 5 ft by 5 ft/10 ft
Special Attacks: Heat, burn, improved grab, constrict 1d8+12, poison
Special Qualities: Scent, elemental, DR 10/+1, darkvision, fire subtype
Saves: Fort +17, Ref +17, Will +7
Abilities: Str 26, Dex 24, Con 24, Int 1, Wis 14, Cha 7
Skills: Balance +24, Climb +18, Hide +14, Listen +12, Spot +12
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Challenge Rating: 8
Alignment: Always neutral
Darkvision: This creature can see in complete darkness, up to 60.
Fire Subtype (Ex): Fire immunity, double damage from cold except on a successful save.
Poison (Ex): Bite, Fort save (DC 25), initial and secondary damage 1d8 temporary Con.
Improved Grab (Ex): When this creature hits with its claws, it attempts to start a grapple as a free action without provoking an attack of opportunity. If it gets a hold, it can constrict.
Constrict: This creature deals 1d6+2 on a sucessful grapple check, in addition to the grappling weapon's normal damage.
Scent (Ex): The creature can detect opponents within 30 feet by sense of smell. If the opponent is upwind, the range increases to 60 feet; if downwind, it drops to 15 feet. Strong scents, such as smoke or rotting garbage, can be detected at twice the ranges noted above. Overpowering scents, such as skunk musk or troglodyte stench, can be detected at triple normal range. The creature can pinpoint locations only within 5 feet. This creature can follow tracks by smell with a Wisdom check (DC 10, +2 for every hour the trail is cold).
Where would I keep her? In a harmless looking basket, of course...