Stapelia hardyi Family: Apocynaceae (Asclepidaceae). A rarely seen Madagascar Stapeliad with brownish green mottled stems. Flowers are most common and numerous in the late summer and fall but can bloom any time of year if happy. They can take some direct sun, but aren't full sun plants. This flower has a pretty powerful scent so you probably want to move it outside when it flowers.
Give lots of light, but protect from hot afternoon sun in summer. During the growing season they can be watered as much as any other succulent (i.e. regularly but don't let the soil stay wet). Keep drier in the winter. Cool and wet or low light and wet are what rot this and all other Stapeliads.
You will receive a plant shown in the last image or one similar. Plants shown in a 4" pot.