An interpreted bytecode where the lower 5 bits of a byte indicate a statement (assign, jump, call subroutine, conditional expression, etc.) or an arithmetic operator (add, subtract, multiply, divide, bitwise and/or/xor, bitshift) and the upper 3 bits indicate the type of the following operand (direct address, indirect address, literal, random range) Assignment ("let") and conditional ("if") statements can consist of arbitrarily-long sequences of operators and operands, with an 0x1f byte indicating "end of statement".
I've discovered near-identical bytecode languages in three Square games now spanning two platforms: Final Fantasy Legend 2, Final Fantasy Legend 3 and Romancing SaGa. So I'm starting to wonder how many more of their games also use it. Rudra seems a likely candidate because AFAIK it was developed by a collaboration of the former-Xtalsoft team that developed FFL3 and the SaGa team.