It is telnet accessible at address crystal.tinymush.org 6886 It's numeric address is 208.42.18.111.
See the documentation for your client for more detailed instructions. Below are some popular clients and how to use them to connect to CrystalMush.
ux% telnet
telnet> open crystal.tinymush.org 6886
Alternatively you can open the connection direct from a unix command line with
ux% telnet crystal.tinymush.org 6886
You can get a copy of it by ftp'ing it from ftp://ftp.tcp.com/pub/mud/Clients/tinyfugue/ (not tested yet)
After you download, install and compile it, then I do it this way:
ux% tf
/addworld -t"Tiny" Crystal char password crystal.tinymush.org 6886
/world Crystal
host: 208.42.18.111
port: 6886
mtp port: 0
and save it. Then select 'Configure' again and select 'Open Connection'.
CrystalMush Homepage