Variegated Triangle cactus:

AKA: Fairy castle, Dildoe cactus, Barbed wire cactus

Acanthocereus Tetragonus Variegata also known as Variegated Fairy Castle is a dwarf, columnar, branching, slow-growing cactus. The stems are spiny, 5-sided, mid-green with creamy yellow variegation which gives the plant that exotic look, perfect for cactus collectors.
The fairy castle cactus rarely blooms. Cacti need perfect growing conditions to produce flowers and the plants in the Cereus family bloom at night.
Fairy castle cactus flowers are large and white, and usually will not occur until the plant is ten years old or more.