Had a discussion recently about how to handle players whose characters have died during a dungeon crawl. One traditional solution, back even to Gygax, is to have new characters appear in the dungeon at the first plausible opportunity, maybe having been captured by monsters or being the remnants of another adventuring party.
I don't really like that solution though. At the very least it messes with the resource management game, to have new characters at full HP, full spells, and full equipment joining the party in the middle of the dungeon as a matter of course. As an infrequent thing, I wouldn't mind too much - meet another party, roll well on reaction, join up, fine. If it were accompanied by some resource exhaustion on the incoming character, that might be fine too. But the stated policy of many DMs, to have new characters join the party at the next possible excuse, does not seem like a policy that I would want to make known to my past (occasionally exploitative) players, particularly in the presence of the Reserve XP rule allowing them to bring in new characters of higher than 1st level.
Maybe the problem here is really Reserve XP.
But in any case, that's not the thought that I came to share. As I mentioned last post, Beyond the Black Gate has been on my mind. Another post of his which has been influential on my thought was about Arneson's impartiality, and this bit sprang to mind:
He would go so far, sometimes, as letting the players roll the dice for both sides of a conflict. Once, when the party's boat was a attacked by a horde of lizardmen, he told us how many there were, their armor class, their hit points, what they needed to hit us, and so on. They were stupid, he explained, and fanatic, and would fight to the death, so we should be able to take care of that ourselves, and he was going to go get a coke and he'd be back in a few minutes to check on us. Half of the players grinned at his audacity (me included), while the other half looked around for the hidden cameras or waited for the punch line.
And Boot Hill's bit about having players with no stake in a particular fight play the opposing NPCs is also fresh. So...
If a player with all dead characters has finished rolling up their next one and is now bored, let them run some of the monsters in combat. Heck, maybe let them direct some random encounters out around the edge of torchlight. I could see this being tricky to do well given partial information - presumably you don't want to show the player the ground-truth dungeon map, because his next incarnation may well come back to this section. But I think having them run, say, an humanoid champion and his goons in a combat is probably pretty reasonable.
When I was first starting to learn to DM, my father did something similar, I think, introducing me to monster statblocks and letting me run a few of them in combat. Granted, that was in 3rd Edition, where the statblocks were a lot more complex, but I still think this might be a reasonable avenue to help players get familiar with how things work on the other side of the screen.