Rift is able to open rifts to pocket dimensions. However these dimensions overlap with ours, similar to the mirror dimension in doctor strange. Time doesn't pass here. As Rift, Ben can enter this mirror dimension at will and open smaller pocket dimensions where he can hide/store stuff. I'd imagine he'd bring armor and weapons using this ability and technically he would be able to fit an entire arsenal of weapons using this pocket dimension. He has scythe-like blades on each arm made of dark matter, and when he energizes these blades with dark energy, they glow a light neon purple and cause slits or rifts in reality that he can expand by putting his forearms together and then expanding them.