First up is mapping from address to file, line and column. This one is basically a custom data compression scheme in the form a custom byte code. Strange but not too bad.

Second is “DWARF expressions", which is Turing complete and used for many things, such as figuring out where in memory or registers a given high level variable can br found at at any point of the program execution. It is baroque to say the least.

Then there is EH frames, which is used for unwinding (on exceptions in C++ or panics in Rust for example). This is used to specify how to find the base of the current stack frame given the current instruction pointer. This is needed if you don't use frame pointers. In itself it isn't Turing complete, but it can call out to Dwarf Expressions as subroutines, so it actually is TC. Except from what I have read, no compiler actually makes use of that capability, thankfully.

Surprisingly, the DWARF specification itself is actually reasonably readable and well written.