Rather than come into play under your control, Xantcha infiltrates the ranks of one of your opponents, before proceeding to wreak havoc on the battlefield
While six mana is enough that I would be surprised if this ability were the primary reason people played the card, it can do some pretty powerful things in the late game and opens up the possibility of Honored Knight-Captain seeing play in an equipment deck
The general wisdom surrounding Gilded Lotus is that, if you can do something that turn with the mana you can tap it for, then its a worthwhile play
Finally, theres a Cryptic Command as a promo, you get one for every $200 you spend
[Darkness] Ferocious Bellow 20 During your opponent's next turn, the Defending Pokemon's attacks do 50 less damage (before applying Weakness and Resistance)
Its an elite institute for the training of the youth of Dominaria in artifice and magic