One of the Egyptian God cards. Slifer is a massive dragon with two mouths that represents the Egyptian god Osiris.
Slifer the Sky Dragon requires three tributes to summon, and has X000 Attack and Defense power. His attack strength varies with the amount of cards it the owner's hand. Slifer also, while face up on the field, when a new monster is summoned, Slifer lowers it's Attack or Defense by 2000. If the Attack equals or bypasses Zero due to this, the monster is destroyed. Slifer, along with Yami Yugi, cameoed in the manga Bobobo-Bo bo-bobo Chapter 104 pages 12 and 13.
Slifer also was the most used by the Pharoah, also being used to make chase after Theif King Bakura and Diabound as well as attack Zorc Necrophades.
In the final duel between Yami and Yugi, Yami at one point managed to summon Slifer, Ra, and Obelisk to the field at the same time, but through an ingenious strategy Yugi was able to defeat his counterparts use of the god cards.
Yu-Gi-Oh! Duel Monsters: Pyramid of Light
A American produced movie to the Yu-Gi-Oh! franchise. It was not very successful in America or Japan.