Hercules is a C-based MMORPG server emulator for Ragnarok Online. It is a multi-process application suite: the login server handles account authentication and IP banning, the char server manages persistent character data, guilds, mail, pets, homunculi, and other account-wide state, the map server runs the real-time game world with combat, NPC scripting, instances, battlegrounds, item systems, and chat, and the API server exposes HTTP endpoints for external tools. All servers persist to MySQL/MariaDB through a shared SQL abstraction and communicate using custom binary inter-server packets. The architecture is modular at the subsystem level through interface structs containing function pointers, which also power a runtime plugin system (HPM). The primary data flow is: client packets arrive at login/char/map servers; map servers mutate real-time game state and delegate persistence to the char server; the char server executes SQL against the database; the API server proxies selected requests through login/char connections. External dependencies include MariaDB/MySQL, libconfig, cJSON, zlib, PCRE, GRF archive files, and bundled HTTP/multipart parsers. The codebase is actively maintained with CI covering GCC, Clang, MSVC, sanitizers, and multiple database backends, and it has recently transitioned toward CMake and Conan. However, it retains significant legacy weight: extensive PACKETVER conditionals, autogenerated packet header files, bundled third-party libraries, monolithic source files, and historical SQL migrations. It is a specialized game-server project rather than a general-purpose library, but several low-level infrastructure components are cleanly separated and reusable.