Improving Attack/Defense/Intellect

[Roman]

Can somebody list all the ways to improve those pemanently?

I can think of:

1) Gaining a Level
2) Finding an appropriate Altar
3) Some items after a certain amount of battles disappear and grant a permanent boost - I had a ring that granted me permanent +3 to Intellect after a number of battles

Is there anything else? For example, there is a way to buy runes, does a similar opportunity exist for Attack/Defense/Intellect?