Giratina

He calls Gothitelle "Mom".

Throughout Hell, which is literally red earth and fire, there are what appear to be the gates of the Underworld, gates which are only the gates of Giratina's house and his mother Gothitelle.

Giratina spends all his time playing on his console, just like Arceus.

Giratina likes to scare newcomers to the Underworld, and while he lets most be tortured, he only takes those he believes to be innocent to his home.

When his jokes go too far and make someone cry, Giratina feels sorry for them, since he's not good at comforting people.

Although Giratina is a hexapod and always walks on its six legs, it only stands on two legs when it wants to intimidate.

Giratina appears to be quite mocking and cruel, especially as the ruler of Hell. He doesn't actually punish arbitrarily; this is evident when he sees some children who were banished to Hell for breaking the rules. Instead, he lets them stay in his house until they leave, wishing them well and hoping they won't return to Hell. So, while at first it seems like he's going to torture you eternally, it's just a facade and a joke he enjoys playing.

In the Starter series, we only see Giratina in its altered form:

In this form, Giratina has an imposing and almost ghostly appearance. Its body is long and serpentine, but with a more solid than ethereal structure. A metallic gray tone predominates on its torso and neck, which is covered in thick, segmented plates that resemble ancient armor.
The front of its chest features horizontal black stripes with intense red details, creating a striking contrast and a darker vibe. Its head is elongated, with a kind of golden, natural helmet surrounding its face, from which several sharp points protrude backward, like a broken crown or thorns.
Her eyes are small and bright red, conveying a cold and distant expression.
From its back emerge six black wings that appear torn or made of solid shadow. Instead of feathers, each wing has reddish tips shaped like claws or tentacles that protrude, giving it a disturbing and supernatural appearance.
Its legs are thick and powerful, with sharp golden claws. Despite its quadrupedal form in this version, its posture remains elegant and commanding, as if it were floating even when it touches the ground.