Finding a nice piece of rock is everything you need to build a spectacular and useful terrain piece, just ready for the Storm of Magic Warhammer supplement
1. Acquire a piece of semi-precious stone
As it comes to rock shapes anything goes.
For my project I used "banded flint", a mineral indigenous to Holy Cross Mountains in Poland, used in Neolithic age as a material for ritual knifes and axes. Currently obtainable as a souvenir from the town of Sandomierz and in other places. I bought mine for an equivalent of 1.50 Euro in Szklarska Poręba (Schreiberhau)
2. Prepare an attractive base
3. Using an epoxy glue attach the stone to the base
4. Mask the glue with static grass so that the obelisk looks like it sticks out of the ground, not just lays on the ground
And that's it, you are ready to catch winds of magic