RTL says if you cant roll enough power dice, and you use a power potion, you can upgrade instead. (for example Karnon, who rolls 5 black all the time can upgrade 5 to silver instead)
Likewise if you use a Doom you can spend that on die upgrades as the OL.
What it doesnt say specifically is for the Titan ability - whereby units get an extra power die... can they take that as an upgrade too? The only case it really matters is the Master Dark Priest. Was the intent that the Titan's ability does not apply to that master, or that master would get to turn one of his blacks to silver, just like all the other cases where additional dice turn to an additional or upgrade?
Is it generally accepted that anywhere you could add a die, that means add a die or upgrade one?