A somewhat strange
die, the d10 is an polyhedron
whose sides are composed by identical
but irregular quadralateral
s; two sides of each face
are short and connected by an obtuse angle
while the other two sides are long and connected by an acute angle
. Five of these acute
angles converge at each point
of the die, while the obtuse
in the middle
In any event, a d10 is generally numbered from 0 to 9, making it the only kind of die that usually has the number 0 on it. When instructed to roll a d10, though, the 0 is treated as if it were a 10. This seems strange until one learns about rolling d100; in this case, one die is the tens place and the other the ones place, and rolling two zeros is considered to be the same as rolling 100.
While this die is used in the various forms of D&D and AD&D, among other RPGs, its real claim to fame is its exclusive use in White Wolf's World of Darkness games. If that setting appeals to you, invest in a bunch of these.