MArcomage

With "same keyword" would mean having the all same keywords or just sharing one? All no keywords means another card with no keyword right?
That would be from all the cards pool right?

Given how it's worded, I assume that it would have no effect when used on a card with no keywords.

yep , no effects on "no keywords cards"
"same keywords" means you can upgrade common Undead to uncommon Undead
cards with multiple keywords like Undead/Charge allow to upgrade to uncommon Undead or Charge