I was in a campaign some years back that involved time travel in its later half. Early in the campaign, before time travel became known to us, one of our first big triumphs was to collect a bounty by killing an old war criminal that had escaped justice. He was a guy called the Butcher of Bracken Ridge who had ordered his troops to massacre thousands of prisoners of war rather than let them go.

Much later on in the campaign we discovered time travel and in one of our flubbed attempts at a targeted hop we wound up in the vicinity of Bracken Ridge, the day before the atrocity was supposed to occur. The way time travel worked you could go into the past and participate in the things going on but if you changed history in a way that interfered with your own personal timeline bad things would happen.

So my character used Disguise Self to disguise herself as the Butcher of Bracken Ridge, went to the PoW camp a day early, and ordered half of the PoWs to be massacred. The other half escaped in the confusion. The next day the “real” Butcher of Bracken Ridge arrived to find the camp deserted and that he was now a wanted war criminal.

It was kind of messed up. I was able to save half the PoW’s lives without screwing up the timeline, which was nice, but I also was responsible for massacring half of them. And also, it meant that the old war criminal we’d killed earlier in the campaign was innocent.

I think on the balance it was a good use of disguise self. But really makes you wonder.