2008 yugioh decks 5D's Starter Deck English "Junk Warrior" Synchro Monster Deck [Toy] : Toys & Games DARK Warrior/Synchro/Effect Monster Level Decks for the 2008 event

It means you can only play one spell a turn as mono blue (aside from your raft of colorless artifacts!), but it means that your one blue spell a turn is uncounterable except for like a Tibalt's Trickery or something in non-blue

Elesh Norn, Grand Cenobite is perhaps the most played card of this cycle, seeing play in Legacy as one of the best reanimation targets in the game against any creature deck

This Simic card plays like a more expensive Pongify, trading efficiency for flexibility as a split card and exiling the creature rather than destroying it

It's just a very useful tool that has a lot of practical applications