The ritual vases or bumba that are involved in a secretive Buddhist ceremony in Mongolia highlight the theoretical potential of centralizing material objects which instantiate doubt in anthropological theory. The uncertainties around the contents of these ritual vases, depending on their origins, demonstrate how doubt reflects broader uncertainties and can be generative of religious practices and imaginaries. Bumbas are thought to instantiate great power if they are treated correctly and contain the right materials. If, however, the material contents are suspected of being inert or repellent, the owner risks being rendered foolish, and the ritual will have no efficacy. Materials instantiating unknown elements and causations can, through their presence, be a source of obfuscation, rather than clarification. This article highlights how the conjunction between uncertainty and material forms can reveal the interplay of certainty and doubt, which, rather than creating internal intelligibility, can constitute open cultural and ritual fields.