Manifesting cards lets you take the top cards of your deck and turns them into 2/2 facedown creatures, instantly letting you refill your board with tons of creatures when you get rid of one big one
Replication Technique technically puts you ahead, but you're better off not giving your opponents anything
Karns Temporal Sundering Karn's Temporal Sundering might be my favorite extra turn spell for Cube
Desecrated Tomb generates Bat tokens when creatures leave your graveyard, which can be more or less relevant depending on your commander
To be fair, this was a rare, unlike the rest of the cycle of 1-mana boons, but I dont think Richard Garfield and the rest of the designers of the early set couldve realized how powerful drawing cards can be
(2021-03-19) If the resolution of a triggered ability involves casting a spell, that spell can't be cast if a spell with split second is on the stack