A plant demon disguised as a human.

(Whee!! I'm a Water Bender!! :D)

The thief character who loves tagging everything around her.

Speaking of tagging...we really need more Ragnarok rogue-esque items around here.

The protagonist character that has had a rough past and was seen as an ungerdog when they were younger and then something terrible/dramatic happened in their lives and they were forced to live a different path and fend for themselves and grew into an independent character trying to set things right.

a Gimmie Cat ;).

A chimaera created to destroy humanity.

(okay maybe I dragged a bit of your story into it Quiet...)

Heh, that's fine ;).

The party mage with the kitty that takes up one held item slot. Wont let anyone else hold it.

....The seeming innocent girl. (Ever watched/read Higurashi?)

Nope.

Demon leader of Wolf Clan, side boss in a long and complicated side quest.

An expert ghost and demon slayer, who looks composed when not working, but becomes deadly serious when she is.

....A bit too epic to be in a game...

The long-lost warrior of ancient times who sacrificed himself to save a land from destruction. The protagonist, after a long series of clues and quests, figure out that the warrior's the key to some great secret/revelation.

Guardian boss who determines whether or not characters are worthy enough to enter a particular area.

The gatekeeper of a mansions during festivities. She'll invite you in (you neeeeed to go there for a quest), but only for a hefty price.

A character that is upbeat and brings the party into good spirits and motivated them when everything seems to be going wrong or there is no hope.

Villain that is really really anoying to kill (see: Majora's Mask Goron temple mini-boss)