either one can help immediately cast the other, and Beledross giant mana reload can give Jadzi the juice to get most of your deck into play the same turn
Plus, there are many different engines you can set up with Grixis cards, with different gameplay options, and thats one thing I appreciate from a color combination
However, if you haven't descended this turn as your end step begins, the ability won't trigger at all
Similar to Interdimensional Web Watch, Goblins Shadow has a reasonable chance to see play in Commander decks that care about casting cards from outside the hand
Theyre great for Storm decks to not run out of gas, and they are easily abused with cards like Hullbreacher or Narset, Parter of Veils that make sure these cards are as one-sided as possible
One of these lands (Karakas) is banned in Commander, another (Pendelhaven) is properly rated, and two others (Hammerheim and Tolaria) have upside so narrow they arent really worth the effort