It's one more mana than Return to Dust and it will always hit two cards, even when you cast it on someone else's turn
To make it worse, Skithiryx, the Blight Dragon can be given haste for one black mana, letting it attack the turn it comes out and can be regenerated for two mana, dodging death and most removal spells
Great ideas, take my suggestions with a grain of salt because really the build I am suggesting is potentially very different from this one
In that way, its hard to properly contextualize just how threatening Thorn Elemental was when used against players who had not accurately understood resource management
Whether youre using +1/+1 counters, Loyalty counters or, really, any counter that can be proliferated to strong effect, like a Poison counter, this card seems quite powerful