Sam and Dean Winchester encountered many demons during Supernatural's run, but few proved as memorable as the now deceased Meg. As Supernatural went on, the Winchester brothers were continuously introduced to denizens of Heaven and Hell, but contrary to what most would expect, not all angels were their allies, and not all demons were their enemies. While demons, by their very nature, can never fully be trusted, they have also gotten Sam and Dean out of quite a few potentially deadly situations.
One of these unlikely demonic allies was Meg, named as such due to her first being seen possessing a woman named Meg Masters, with her true name never being revealed. Meg was portrayed in early seasons by Nicki Aycox, but her longer-term incarnation was played by Rachel Miner, who is best known outside of Supernatural for playing Dani on the David Duchovny comedy Californication. Miner took over as Meg beginning in season 5 and played the character off and on for the next three seasons.
Meg eventually developed a reluctant alliance with Sam and Dean while particularly bonding with Castiel, teasing a romantic relationship between the demon and angel. Sadly, Meg gets stabbed to death by Crowley in the season 8 Supernatural episode "Goodbye Stranger" after helping Sam, Dean, and Cass thwart Crowley's latest evil plan. Unfortunately, the real-life reason for Meg's departure from the show was Miner's struggles with multiple sclerosis. She was diagnosed with the illness in 2010, and by her 2013 Supernatural exit, she was having difficulty performing the role. In a show of respect, Meg was never recast.
Rachel Miner's Supernatural Season 15 Role Explained
Thankfully, Rachel Miner's Supernatural story has a happy ending. While she never reprised the Meg role, Miner did return for a few episodes during season 15 leading up to Supernatural's series finale. While Miner's new character looks like Meg, she is actually playing a physical manifestation of The Empty, a timeless being that resides in the void where supernatural creatures go after death.
In a nice touch, The Empty initially used the Meg form to taunt Castiel, who had woken it from its eternal slumber and left it enraged by the whole situation. Many long-time viewers of Supernatural were resoundingly happy to see Miner back onscreen, even if Meg herself was still presumably residing within some section of Hell. After Jack became the new Supernatural God and remade the world late in season 15, though, he likely facilitated a better fate for Meg since she died on the side of good.