Final answer:
Mephistopheles grants Faustus access to worldly pleasures such as sex, power, and knowledge in exchange for Faustus' soul, embodying the concept of a Faustian bargain.
Step-by-step explanation:
The specific request that Mephistopheles is fulfilling in exchange for Faustus' soul in Johann Wolfgang von Goethe's version of the German folktale involves providing Faustus with access to all worldly pleasures, which include sex, power, and knowledge. In return, Faustus must surrender his soul to the devil after a predetermined number of years.
This narrative, known as a Faustian bargain, has become a cultural metaphor for the dangerous trade-off between immediate gratification and ultimate ethical or spiritual loss, reflecting a common theme across various cultures and historical contexts regarding the allure of wealth and power at great personal cost.