For my Thaumaturgic magic system I chose five elements
- Fire (Heat).
- Force. Which includes Alchemy, by using vibration to warp the structure of matter.
Other abilities such as teleportation, and physical augmentation are all non-elemental.
I chose the word entropy because it sounds cool, and the name is more distinct than necro-something. The name is all so closer to the power that I want the are not to have, it doesn't control the force of death, manipulate the souls of the dead or allow the creation of zombie.
Entropic magic is all about erosion and dissolution, fires go out, stone turns to dust, metal corrodes, wood and flesh rot away its touch. The problem is that the other elements all do the same thing, just only within their domain. Entropy can affect everything it's just a matter of targeting, it takes without giving back.
Thus leaving the element of entropy without distinctive feel to me, the only unique thing that entropy possibly could do is tamper with probability. The problem is the ability to rig the game, is very, very dangerous and mechanically speaking one of the most unbalanced powers to allow.
I already have people that can influence probability, the clerics, priests and shaman. Divine magic in my setting is probabilistic in nature. Through their connection to their respective deity or deities a priests can touch the wyrd and can bless or curse things within their gods purview. Tying the ability to affect the roll of the cosmic dice to a deity's purview was my way of constraining the ability, entropy though would only cause disorder (errant luck) would affect everything, thus being unbalanced.
Aside from affecting probability through chaos what could entropy do that's distinctive, and if we stick with probability how do we limit its scope.