Me and my crazy ideas! Came up with an idea to mesh a couple of my passions into a routine: Dungeons & Dragons inspired RPG mentalism trick. The idea is that the spectator takes on the roll of our heroic character right at the climax of the big boss battle, slaying the dragon in an epic way. This then fulfills the "prophecy scroll" introduced at the beginning of the routine, which is a perfect recount of their choices and exact die rolls.

SO... my first thought is I want to have them roll a "critical hit", which is rolling a 20 on a d20 die. I've found people talking about loading die and melting them and such, but everything I find talks about the standard d6 dice. Does anyone have ideas or has done something similar before, with forcing die rolls? The restrictions is that this has to be a single roll, and it always has to roll 20 perfectly, so no "elimination die" or using the sum of both sides or anything like that. Has anyone had experience with melting or loading dice, magnets in a dice tray, or other methods for forcing a specific roll? Any thoughts on where to find information or how to pursue this would be much appreciated.

Magnetic dice.

I've melted d6s and it helps but isn't a sure thing