With Rionya, you can just send the token in, and if it dies to a blocker, you can just send another at the beginning of the next combat phase, infinitely
Sure, they could spend a little extra mana to waste a burn spell on it after you block, but you still come up on top by having the Curtains absorb a spell instead of your life total
Now that extra caveat is out of the way, its time to talk about Palantir of Orthanc properly
Whenever equipped creature attacks, venture into the dungeon
Considering you're facing three opponents and all four of you will keep sacrificing your creatures again and again, you'll create a lot of extra mana, which is essential because black is not exactly known for its ramp
Selling Magic cards doesnt always have to be as tragic as falling out with the game and pawning off an entire collection