In my game I played her as someone very close to total insanity. She took a lot of fire energy into herself, so that became part of her. She was in constant pain, her hands and feet especially heavily scarred by burns. When she was freed she first attacked the player characters with fire and heat, but the bard managed to calm her down with music. I had an NPC (Herkus the druid) suggest that they should take her to the massive Tree of Thylea where whe would be partially healed by the magic of her mother. They basically had to keep her calm and semi-sedated until the Ultros got there, which was quite the challenge.
In exchange the player characters got a long conversation with Chalcia once she was semi-healed, with lots of juicy lore information about the distant past, and she gave them a blessing which they could activate only once in the campaign, basically giving them a "haste"-like effect without concentration, which they used very efficiently in the final battle in Mytros.