Epiphyllum Guatemalense Monstrose / Orchid Cactus
This guy is a jungle cacti native to Guatemala.
It's an epiphytic cactus that attaches itself to a tree and live off of the composting debris that collects in the crook of the tree. Epiphytes are basically parasites that don't damage the plant they're living on.
Epiphyllum guatemalense 'Monstrose' are commonly called Orchid Cactus due to the blooms resembling orchid blossoms. Its blooms are one of its endearing features. However I love these guys for the curly, wurly stems.
Place your cactus in bright, filtered light, with moderate to high humidity. To increase the humidity, position the pot on a tray filled with gravel and keep this topped up with water, but not enough so that the water reaches the surface.