At the time, Gates of the Underworld Structure Deck and the overall archetype was quite a hit among the players as it featured two monsters with very high power which can be Special Summoned once discarded to the graveyard by a card effect
[3] Once per turn, during your Main Phase: You can take 1 "Toon" Continuous Spell from your Deck, and either add it to your hand or place it on your field, face-up
Cubic Ascension and Cubic Causality provide a defensive layer to the deck while also having strong Graveyard effects that let you reverse the flow of the game
That alone makes it an amazing card, but it also can flip and set cards already on the field, setting their monsters' effects up to activate during the next turn or during the opponent's turn if they think they can destroy it
EDT on Wednesday, July 30
They only existed in the TCG, and were discontinued after Ancient Sanctuary