1)Create a Tree of Skill as in Diablo 2
Place a tree on the map and add some fx to it so that it is distinct from the surroundings. Create an event of 'Upgrade Hero' when 'Enter area' on the tree location. Add some dialog to spice up the event.
2) Create Shrines.
Place a small area of water (Brush no: 2 i.e. the medium brush in the editor) on the terrain (not underground and shadow world). Now, switch to the small brush and select pillars from the caverns part of terrain ( the thing that whole of the underground is made of) and place it in the middle of the water. The terrain will elevate. Now place grass in place of the pillar. Switch on to the rocks in Grass tab of the terrain and place them over the grass. This will give it a realistic feel. Add some monks (normally 4 nos) surrounding the elevation from all the sides. Add torches to give some extra effect.
-> To make it more interesting, u may add 'Play Fx' or 'Storm' effects when player is nearby to the shrine.
-> To make it additionally interesting, u may add 'Spawn Unit' effect when player is nearby to the shrine.