Improving Attack/Defense/Intellect
 

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?

Always try to 'use' quest items, sometimes they provide stat bonuses.

Interesting - I didn't know that - thanks! I may already have missed out on some, as I have completed many quests already.

I didn't know that either - thank you for the tip man!