I don't know what kind of game this would work in but looking to participate even if you do not want someone every week. I played runequest 15 years ago, but haven't done rpgs since.

I am looking for something interesting and I don't know if it would fit in with your desired group.

On the outside I look like a young adult women with a missing arm, missing eye, and large wounds that have scarred over on the side of my head. I wear a white robe, and offer to help my group with healing and other services along with a useless hireling, goblin or orc I don't know. When I am sure no one is looking, I unleash my powers to destroy the party's opponents.

What they don't know is that I am in fact a tiefling half fiend that is chaotic evil, but enjoys being in groups with fellow adventurers.  I had my masters saw off my horns and prepare me for offering to their demonic masters along with my siblings.  In the last moment a competing demon offered me the power to get revenge if I would serve him.  I did make the pact, and was given strength to kill my masters which set me on the path to eternal servitude.

I would love to participate from time to time as a side character if possible to help with hard dungeons etc, as well as serve my sponsoring demon by killing members from other religions that oppose the group.

My backstory is that my demon sponsor has gifted me with long life, and I generally enjoy participating with raiding parties as well enjoy the protection it provides against those who I have wronged.

I find that over the years, the more I protect my party, the better the chance for my survival, so despite being evil, I fight to keep the party together, and am willing to go on quests to do good to avoid arousing suspicion among the party.