They might have enough damage to threaten lethal next turn through the use of extenders and the many summoning mechanics in the game
If a card is discarded while Rest in Peace is on the battlefield, abilities that function when a card is discarded (such as madness) still work, even though that card never reaches a graveyard
I play a Rakdos sacrifice deck in Commander, and you can bet that I'll be hoping to pick Sephiroth, Fabled SOLDIER for my deck once its price [hopefully] settles down
If any of those monsters were from the Extra deck, theyll have to sacrifice all of those materials again too
Also known as the Chemmy, Irish, wash, scramble, hard shuffle, ice cream, smooshing, or washing the cards, this involves simply spreading the cards out face down, and sliding them around and over each other with one's hands
Remember to prioritize though