Lady Sia

An action/adventure platformer for the Game Boy Advance released in 2001.

The titular character is a warrior princess who needs to defeat an invading force of anthropomorphs called the T'soas created by a warlock named Onimen. She travels through four areas, each with several levels as she retrieves her stolen sword and magic ring, reforms alliances with the leaders of the elemental realms of fire, air and water, and continues on to remove Onimen from her palace.

Also of note is Sia's shapeshifting abilities; in three out of four major boss battles, she transforms into a humanoid beast with claws, superhuman strength, and a mane of hair. Why? Rule of Cool , probably.

Not to be confused with Sia the musician.

Tropes used in Lady Sia include:

Action Girl: Sia herself.
Cool Sword: It's jade. Need we say more?
Development Hell: A sequel was planned in 2003, then got cancelled and is now trapped there forever.
Idle Animation
Multiple Endings: The true ending is only unlocked after getting a perfect score on all stages, unlocking the bonus stages, and then getting a perfect score on those.
Narm: Right before the last fight, the Final Boss says, "You will die an ugly teddy bear, girl!"
Nintendo Hard: A short health bar, enemies everywhere, and glitches in vital places.
No Ending: You beat the last boss, he changes into a massive demon with wings, and...flies away. If you did not unlock the true ending, the game ends and the credits roll.
One-Winged Angel
Transformation Sequence: A short one, used when Sia transitions from normal to what's usually called her 'sasquatch' form.