For example, you can't cast a creature card with mayhem you couldn't normally cast during an opponent's turn, even if you discard that card during an opponent's turn.
While mainstay decks like Tolarian Terror, Madness, Affinity, and Jund Wildfire are still as present as ever, there's been a lot of churn with decks like Elves, Mono-White Aggro, and Tron making big comebacks
Its value depends on its condition, market demand, and language (Japanese versions may be more valuable)
They are very consistent, and The Phantom Knights Of Break Sword can make all their Level Three Monsters into Level Fours, of which is the Level Rhongo needs to be Xyz Summoned
Sealed Products English Pokmon releases are somewhat infamous for including a large quantity of additional sealed products
Different types of Tron decks use this in different ways, but the core principle remains the same: find those Urza lands fast