MLIR is now an inherent part of the LLVM compiler infrastructure, but what connects the two representations? In theory, the conceptual similarity of the core representation. In practice, a highly important, yet often overlooked, module translation subsystem. This talk will present the multi-dialect translation mechanism available in MLIR to target LLVM IR, explain how to use it for a custom dialect, and argue why it may not always be the best idea. It will also discuss interoperability between MLIR and LLVM IR functions, including ABI for built-in types and calling conventions.