Considering that Nissa, Worldwaker is available to use outside of the beta, I feel that this can be discussed on the forums.
Ghalta’s interaction with Nissa, Worldwaker’s 2nd ability, Worldwake, is bugged.
If you just try to give Ghalta mana with the Awaken ability on him, he won’t gain any additional mana and will just go to the field without triggering the effect. I dumped a Hour of Promise cascade into a Ghalta that needed 2 mana. It gave him 2 mana and the rest went nowhere.
If you instead disable Ghalta in hand first, he will take the additional mana towards Awaken; however, at that point when you re-enable him in your hand, he will now cost an additional 4 mana for the 4 mana you just gave him towards Awakening, even though his mana is full.