This comes from Michael Lawrie's "Confessions of an Arch-Wizard"
MIST was a MUD (see the MUD FAQ if you're not familiar with MUDs). Wiping refers to deleting a character.
Not many games seem to have much in the way of irritating features
that totally destroy any concepts of fairness, MIST's pistol was
probably fairly unique in this. The theory was that when you got to
legend (one level below wizard) you could get the pistol and play
Russian Roulette. If the pistol went off, you got half the points
needed to get to wizard and if not you died... dead. The only problem
was that it never quite got round to giving you the points if you won
and so basically it was left to the discretion of wizards or arches.
As the wizards lived in fear of giving players too many points (they
tended to just get wiped without question) they weren't often willing
to comply. As an added bonus, a legend could be forced by a lower
level character to shoot themselves.