Cut or tear the ancho chilies into 2-inch or so pieces, discarding the seeds and stems. Place in a dry skillet over medium heat and toast for about 5 minutes, just until fragrant, without allowing them to burn.
Transfer to a blender, add 5 cups hot water, and blend until smooth.
Heat the oil in a stovetop or electric pressure cooker, uncovered, over medium heat until it shimmers. Add the onion and garlic and cook, stirring frequently, until the onion turns translucent, about 5 minutes.
Add the salt, pepper, oregano, cumin, and paprika and cook, stirring until very fragrant, about 1 minute.
Stir in the red kidney and black beans, along with the ancho mixture, plus more water as needed to cover the beans by 1 inch. Lock on the lid, bring the cooker up to high pressure, and cook for 45 minutes if using a stovetop model or 55 minutes for electric. Let the pressure naturally release, then open. (Alternatively, you can make it in a Dutch oven: cover and cook over low heat until the beans are very tender, up to 4 to 5 hours, stirring occasionally and adding water if the beans seem dry on top.)
Use a masher to lightly mash some of the beans in the pot, leaving some whole while thickening the chili. Stir in more water to loosen, if necessary, and add more salt and pepper to taste.
Serve warm, with the accompaniments of your choice.