yugioh stardust accelerator decks / Synchron Deck from 𝓥𝓮𝓬𝓽𝓸𝓻 5D's Stardust Accelerator Promotional Cards

Its best effect activates when an opponents monster attacksBrunhilde loses DEF and makes all Valkyrie monsters immune to battle destruction for the remainder of the turn

Expurrely Happiness X LIGHT Rank 7 [ Fairy / XyzEffect ] ATK 2500 DEF 1100 2 Level 7 monsters You can also Xyz Summon this card by using a Rank 2 monster you control with 5 or more materials

Cards with effects that send a monster from the Deck to the Graveyard, such as "Foolish Burial", are used to populate the Graveyard with "Skull Servant" and cards treated as such in order to increase the ATK of "King of the Skull Servants"

So credit is given where credit is due

Playing Lands And Making Mana As mentioned, mana is produced by land cards