They reward the defending, lower-Life player and punish reckless attacking
A big part of that comes from Zimone, Mystery Unraveler, who is such a terrifying commander, able to cheat giant creatures onto the board, and facedown, which will always leave your enemies second-guessing
Chaos Orb destroys any cards that it touches when it lands, whereas Falling Star deals 3 damage to any creatures it touches when it lands (and also taps them) and has no effect on non-creature cards
Use this to surprise your opponent by recasting a cheap removal spell or a counter
* Destroy target artifact or enchantment
Mortuary Mire, Witch's Cottage, and Haunted Crossroads can be part of game-winning sacrifice engines, and putting such easy recursion on a land just asks for trouble