The tag "quest-failed" refers to a porn video where the protagonists are attempting a sexual conquest or challenge, but they are ultimately unsuccessful in achieving their goal. This can involve various forms of roleplay or storytelling in which the characters may face obstacles, setbacks, or simply change their minds about pursuing their objective. The tag is used to convey the idea that the quest for sexual satisfaction has not been completed successfully and might be linked to themes such as denial, unfulfilled desires, or disappointment.