The theory behind curled foils is that humidity changes the fibers of the cardboard, causing it to bend, expand, or contract based on how much moisture is on the card
These big display cards are so wild, the colors pop like crazy when you tilt them
"When [...] would leave the battle area" refers to when that Digimon is placed in the trash, returned to the hand/deck, placed in the security stack, moved to the breeding area, or placed under another card
You simply play permanents that go to the graveyard, most easily by self-sacrificing
When this card is Special Summoned by its effect: You can Special Summon 1 Level 4 or lower monster from your GY, but negate its effects
With cards like Baronne, Chengying and Swordsoul Blackout, the player has to carefully work around their Quick-Play Spells