Say I wanted a 16-sided die with either A, B, C or D on each side, with the following probabilities:
A. 1/16 B. 7/16 C. 3/16 D. 5/16
I could roll the die and get either A, B, C or D with above probabilities. However, I read that 16-sided dice are not isohaedral: not every side can have the same size.
Now consider a 20-sided die (one of the Platonic solids) with the following probabilities:
A. 1/20 B. 7/20 C. 3/20 D. 5/20 E (null reroll). 4/20
Four sides now have a value of $E$, which is void and results in a reroll until either A, B, C or D are obtained. Does this have implications on the probability of getting each of the valid results? Would using the 20-sided die be similar to using the 16-sided die with equal size sides?