Critical failure!

[jaydubs]

I hate mandated critical failures. The characters aren't incompetent.

That said, I take a roll of natural 1 as an incentive to get more descriptive.

My gnome warlock teleported to get line-of-sight on a target, and cast an Eldritch Blast. Natural 1. I described it as his timing for this precise arcane maneuver being slightly off, and the blast firing before the teleport was complete, causing the energy to fly off at a right angle to reality.

We moved on. Later, someone else rolled a natural 1, and I jumped in to say that their attack had been spoiled by a blast of energy flying past their head... my warlock's spell, re-entering reality.

Relatively little in the way incompetence or lasting effects, just a cool mental image.

I really, really like this. I'm going to try to incorporate it into my DMing from now on, though I doubt anything as elegant as an eldritch blast re-entering real space is going to come up.