Lillian is the "baby" of the family and is therefore a bit spoiled. Her parents baby her a lot, and expect Cornelia to do it as well. Although Lillian looks up to her sister and likes to "hang" with her, the two sisters are usually mean and spiteful towards each other. Lillian feels sad about Cornelia's attitude towards her, as showed in "U is for Undivided". But Lillian and Cornelia do care for each other and can be quite nice with one another. They even have similar personalities when you think about it. Lillian also likes to hang with Cornelia's friends, she thinks they are cool and they are nice to her.
During the second season, it is revealed that Lillian is the Heart of Earth, the center of mystical power on Earth. This makes her very powerful, with power equal to Elyon Brown's and the Heart of Kandrakar's. Perhaps that's why Cornelia had been chosen to be the Guardian of Earth to be wise enough to help her sister. But Lillian's powers developed prematurely and she is unable to control them because she is too young. Lillian's powers are discovered when, after being scorned by Cornelia, Lillian wishes Napoleon could talk. After Lillian leaves for her room, Napoleon comes up to Cornelia and says that Lillian's got something special. After consulting Luba in Kandrakar, they discover Lillian's position as the Heart of Earth and Napoleon's position as Lillian's familiar. Once Cornelia is told by Luba that Nerissa would attempt to befriend Lillian as she did with Elyon, outraged Cornelia demands that she be taken immediately straight home, as nobody is allowed to mess with (let alone harm) her sister other than Cornelia herself.
After Lillian causes much confusion by unknownly using her powers to turn a bedtime story Cornelia tells her about a Princess Lillian, an Evil Sorceress Nerissa and the Princess's four protective faeries into reality, Cornelia tells Lillian that to protect herself, Princess Lillian of Earth gave her powers to the Noble Knights of Earth: Sir Matthew, Sir Huggles and Sir Napoleon, until she is old enough to use them. Lillian still thinks it's all pretend play, and with a toy crown and a toy wand endows her knights with her powers, unknowingly making them the Regents of Earth.
Lillian remains unaware of her status as Heart of Earth and doesn't know about Magic, Kandrakar, The Guardians or other worlds. However Cornelia secretly whispers to her sleeping sister that she pledges to always be there for her younger sibling to make sure nothing ever divides them again.
It has been shown that with her power, Lillian or the Regents have the powers of:
- Reality Warping.
- Turning drawings, thoughts or even stories into reality.
- Create zones were the reality follows her wishes and rules and might be different from the outside world. The zones are surrounded by an invisible wall, and look normal from the outside. When one steps into the zone, he automatically become part of its reality.
- Endow others with powers.
- Give objects and animals unusual abilities, such as the ability to talk.
- Super speed and Super strength (Napoleon and Huggles).
- Generate rays of energy (Matt).
Following the examples of all other mystical Hearts shown, Lillian can also probably open folds in time and teleport, as well as have the power to create impenetrable prison bubbles.