Theos is a cross-platform build system designed primarily for developing iOS jailbreak tweaks, tools, and applications, but also supports macOS, Linux, and Windows targets. It is built entirely on GNU Make, with a modular architecture that separates master (top-level) and instance (sub-make) rules for parallel building. The system includes a Logos preprocessor for Objective-C hooking, a NIC (New Instance Creator) for project scaffolding, and packaging support for .deb, .rpm, .pkg, and .ipa formats. Key entry points are `makefiles/common.mk` (main include), `makefiles/rules.mk` (compilation rules), and `makefiles/target.mk` (target parsing). External dependencies include Xcode (macOS), LLVM toolchains (Linux/Windows), Perl, and dpkg-deb. The codebase demonstrates high craftsmanship in its Makefile patterns, schema-based variable overrides, and modular design, though it relies on several submodules and has some legacy components (e.g., Cygwin support).