Hindenburg is the crash handler (for... obvious reasons ^^)
.
Fickel is barely used anymore.
The basic idea is that if you want to kill nickel, you *have* to kill the full set of *el daemons + hindenburg to avoid sickel throwing a tantrum
.
(PS: The canonical source for that list is the
KOReader startup script, as how the environment of whatever kills nickel is set dictates whether you'll be able to restart it sanely without having to reboot).