Personal Gain

A common theme during Charmeds run was that good magical beings are not allowed to use their powers for personal gain', at least not without risk of backfiring.

The nature of a backfire can vary. It can range from losing any benefit gained from use of a spell to someone being killed.

In the case of good witches, personal gain is considered to be a serious breach of the Wiccan Rede. The first to discover this was Phoebe Halliwell, when she used her premonition power to find out the winning lottery numbers. Unfortunately for her, the numbers on the winning ticket faded away after they were announced on television. Ironically, Phoebe's successor as the youngest Charmed One, Paige Matthews, was also the first to experience a backfire after the Charmed Ones were reconstituted. She cast a "karma" spell on a coworker who'd been making lewd comments to women, intending to give him a taste of his own medicine. However, the spell also significantly enlarged Paige's breasts, making her the object of ogling as well.

This rule also appears to apply to neutral beings as well, based on what happened to Cole Turner after he briefly became an Avatar. He insisted on using his newly-minted powers to warp reality in a last-ditch effort to get Phoebe back. To do this, he created an alternate reality in which Paige had been killed shortly after Prue's death. However, as a result of this spell, he lost all of his Avatar powers, reverting instead to the form of Belthazor. He thus created the circumstances that led him to be vanquished once and for all.