clearstream
(He, Him)
I've never witnessed a "completely, totally, absolutely arbitrary" GM and I really wonder if you have?Yeah. The mechanics only tell you the result. It's completely up to the GM--completely, totally, absolutely arbitrary--what that result actually means, how that result happened.
Player "I attempt to pick the lock"
GM "The door turns into a canary and you are smitten by those tufty yellow wings. The house behind the door has gone somewhere else I'm really not sure where oh look, you've just turned into a shoe."
Rather GMs have the job of saying something that follows. In D&D, they "narrate the results of the adventurers' actions", not whatever the heck they like. They're part of the means D&D expects to be used for fabricating the play.
Nothing prevents the GM from saying my character has turned into a shoe... but none have ever done so. This extreme view of GM arbitrariness sets aside some of the normal preconditions for a game to be played. The commitment participants have to the shared experience. GM narrates something simulative (if that is what the group is about) because they've committed to doing so.Nothing actually prevents the GM from saying it was meddlesome pixies, except the GM herself. Genuinely nothing.