A modular which I designed after being inspired by test-folding some of Meenakshi Mukerji’s new single-sheet designs based on the Four-Sink Base. There is a color change between the hollow cones and their background.
This is a classical locking mechanism with two flaps and two pockets as in Sonobe units, so any Sonobe-compatible shape can be made with it.
The unit is named after a supposed pair of ancient pagan deities, two brothers being the Slavic counterparts to Castor and Pollux. I use just Lelum to call a variant of this unit which has only one cone where this one has two.