The curse of the Lyonsbanes had been passed down through Kelemvors family for generations. Kyle Lyonsbane was the first and only of the Lyonsbanes to receive the curse due to his own actions. All those who followed received it from his tainted blood and through no fault of their own. Kyle was known as the quintessential mercenary: every service had its price and he was utterly ruthless in extracting payment, even from grieving widows if they held the gold that he was entitled to.
Kyles actions caught up to him in a great battle, when he was given the choice of defending a fallen sorceress or continuing to cut through the enemy to reach their stronghold and be the first to plunder the vast riches within.
With Kyles help, the sorceress might have gathered her strength, but the mercenary knew she would object to the plundering and could see no clear gain in helping her. He left her to die at the hands of the enemy. Before she died, she spat out one last intricate work of magic and cursed him to pursue his fortunes in a form more suitable to his true nature than a human shell could ever be.
When Kyle arrived at the stronghold and attempted to take his share of the gold, he felt a sudden weakness. He dragged himself away to a secluded chamber where he changed into a near-mindless, snarling panther. Instinctively, the beast knew it had to escape the stronghold. Only after half a days flight from the castle, when the beast had killed a traveler, did Kyle suffer the painful transformation and become human once again.
For the rest of his days, Kyle Lyonsbane suffered the curse of the sorceress: whenever he attempted to perform an act for any type of reward, he became the beast. And even though only selfless, heroic acts were permissible for the mercenary under the curse, he had sworn he would never devote his life to such activities. He was forced to retire from the mercenary life he loved the most and live off the gains he had made from his previous adventures. When his gold ran out and the only avenue open to him was to live off the charity of his wifes family, he took his own life rather than live with the humiliation of poverty or perform any good deeds.
Before Kyle died, he sired an heir to his misfortune. Strangely, when the curse finally revealed itself in Kyles son, the effects were reversed. Kyles son could not perform any act, unless it was to protect his own life, without the promise of some type of reward. If he performed an act and did not receive his reward or he dared to perform a charitable act for no reward at all, he became a panther and was forced to take a life.
A roaming mage had a theory that as the original curse was meant as a punishment for evil and greed, and as all babes were born into the world as innocents, the curse found no evil to punish, and instead altered itself to punish the innocence and good in Kyles son.
The intent of the sorceress curse had been undone, and a long line of mercenaries with histories as bloody and unscrupulous as Kyle Lyonsbanes were born. It was Lukyan, Kyles grandson, who discovered an inherent danger in his fathers condition as his sire grew old and senile: the aged mercenary could no longer remember when a reward had been offered or warranted, or even when or if it had been paid. Because of this, the old man changed into the beast without provocation, and became a menace to all he came near. It became the responsibility of every child in the Lyonsbane clan to slay their father when they reached fifty summers.
Reference: goddesses-and-gods.blogspot.com