This Pokmon has been known for being released on very strong cards (especially for anybody who remembers Greninja BREAK from a little while back)
After that release, Slifer continued along with the other Egyptian God cards through Konami's Legendary Deck collections and further promotional collections
Successfully attacking directly causes the opponent to discard one random card from their hand, disrupting their strategy
Some of those dual sets include To Have Seen the Battle Rainbow [SM3H] / Darkness that Consumes Light [SM3N], Skyscraping Perfection [S7D] / Blue Sky Stream [S7R], and Snow Hazard [SV2P] / Clay Burst [SV2D]
Split cards have both their sides names, their mana value is the sum of both sides mana values, and their colors are the sum of all their sides' colors everywhere other than the stack
It is the kind of card that makes collectors stop scrolling because it looks fun, expressive, and slightly ridiculous in the best possible way