Threat of Darkness Demon World is a Japanese Booster Pack in the Yu-Gi-Oh! Official Card Game. It is the fifth set of Series 3.
In other languages, this set is amalgamated with Power of the Guardian to create Dark Crisis.
This is the first set to identify "Archfiend" as an archetype and as such contains more "Archfiend" monsters and support cards. It includes the chess-themed "Archfiend" cards and an Ultimate Rare reprint of "Archfiend of Gilfer". It also contains cards from the Battle City arc, mainly the ones used by Ishizu Ishtar.
Each pack contains 5 cards and each box contains 30 packs.
There are 53 cards it total, or 57 in the Master Set.