Where did this card come from?

I've been looking into commanders and noticed the card, Xavier Sal, came from the Caverns of Ixalan commander set. But non of the precons are in his colors. So what pack specifically can you find him in? Is it the in-box collector sample? Or is he a bonus from the actual Caverns of Ixalan packs?

I've been looking into commanders and noticed the card, Xavier Sal, came from the Caverns of Ixalan commander set. But non of the precons are in his colors. So what pack specifically can you find him in? Is it the in-box collector sample? Or is he a bonus from the actual Caverns of Ixalan packs?