These are usually unauthorized stickers made to look mostly like a real card
Yu-Gi-Oh is More Complicated by Default than Pokemon One of the most common knocks against the Pokemon TCG is its simplicity
TCG: 25th Anniversary Rarity Collection II Yu-Gi-Oh
Unfortunately, far too many of those articles suggest using desiccant to "keep the cards dry and prevent curling." It's a noble attempt to solve the curling issue, but it brings an underlying assumption that the default state of the cardboard side of foiled cards is "dry." In reality, it seems the average moisture level of the cardboard is around 6065% when printed

First, the champion, playing Mono-Black Necro Control: Creatures (7) Lands (23) Spells (30) 4 Nevinyrral's Disk 1 Hymn to Tourach 4 Necropotence 1 Ivory Tower 4 Dark Ritual 4 Drain Life 3 Stupor 2 Mind Warp 3 Contagion 1 Serrated Arrows 2 Demonic Consultation 1 Zuran Orb Sideboard Then, in third place, representing the aggro decks of the format, Brian Hackers Bad Moon Necro: Creatures (19) Lands (21) Spells (20) And then finally carrying on the fine tradition of B/r Necro-decks, Chris Pikula, who actually increased the red presence in the deck with Incinerates and multiple maindeck Shatters (Winter Orb, Howling Mine, Serrated Arrows, even Black Vise, Ivory Tower, and Zuran Orb were worthy targets)
Experimental Synthesizer A 1-mana artifact that pulls two cards from your library and creates a 2/2 token by the time it leaves the field is amazing value in Pauper