The release date on mutations for players has yet to be announced and confirmed, and will not be coming out any time soon (supposedly longer than 8 months). Take the information on this page with a grain of salt and not to be taken as fact.
According to the game's trello and subreddit, it is planned that a player would be able mutate their magic at level 300 and god mutations at level 400. Contrary to what some may think, mutations are not a combination of the First and Second Mind, instead they are both completely independent when choosing mutations.
The First Mind Magic may normal mutate or god mutate at level 300 and 400 respectively. Second Mind Magic may also normal mutate and god mutate, though only if the First Mind does not already house a god mutation and vice versa. The Third Mind Magic cannot mutate at all. If the player wishes so, they may choose to not god mutate either of their First and Second Minds to house normal mutations instead.
The chart shown above is mostly outdated, and there has not been any other mentions of a newer chart.
Click here for the creator's early words about mutations on this trello page.
Verdies, Angry Pirate Captain - Plasma Magic
Theos, The War Phoenix - Sun Magic and Phoenix Magic