Every time you pay 4 life the next time Library activates it will be giving you more information and better card quality than it otherwise would much like having a shuffle effect
For example, this means that normally, if you control Hunting Velociraptor, you can cast Grim Giganotosaurus for its prowl cost only if a Dinosaur dealt combat damage to a player, but if an effect causes the spell to have other creature types, the prowl ability is also satisfied by a creature with those additional types having dealt combat damage to a player
You can only activate 1 "Over Fusion" per turn
Following their dominance from the previous format, Tearlaments and Spright continues to ravage the OCG 2022.07 format with further support from Darkwing Blast
Free things are great, sure, but this mechanic also instills a weird sort of fear of missing out that makes you feel like you're almost losing money by not logging in for a single day