absolutly can not, it is obvious in the rulebook, one upgrade per attributes.
I think it encourages player to make decision, long investment by choose to upgrade +2 per attributes (but you have to do it 3X or by +1 for two attributes.
Anyway I suggest you upgrade your hero once, he is more useful to explore the map or duels other hero (only health does matter) rather than just stay to upgrade, remember you can only do quest once per year, the sooner finish the quest the better chance you can get runedragon
I think it encourages player to make decision, long investment by choose to upgrade +2 per attributes (but you have to do it 3X or by +1 for two attributes.
Anyway I suggest you upgrade your hero once, he is more useful to explore the map or duels other hero (only health does matter) rather than just stay to upgrade, remember you can only do quest once per year, the sooner finish the quest the better chance you can get runedragon