When magic first started, Wizards was a far smaller company and pulled ideas for sets from history or, in the case of Arabian Nights, a book (One Thousand and One Nights), which gave way to cards like Ali Baba
A reasonable approximation of the expected power of gold cards is that your 2nd colour of mana adds about a 1/3rd of a mana, the 3rd colour adds 2/3rds of a mana and the fourth is a whole extra mana
Specifically, Zur, Eternal Schemer will rotate out when Edge of Eternities is released
Download Goblingram today, and you'll be making enemies in no time
Focusing on damage may not always be the efficient choice in Commander, but multiplicative scaling certainly is and I love how Obosh can give an immediate nitro boost to traditional red burn and creature aggro to help those classic strategies threaten powerful Commander tables