The sudden mutation of Katu I think is a memorable point for many people. Because just from the perspective of Katu, it is really too scary. However, this card belongs to the ten generations of jun in the anime, and the ten generations often use this card to make the elemental heroes on the field become enhanced forms, so if you understand the anime, in fact, the card diagram of this card will not be so resistant. And the effect of this card is indeed a very powerful existence, strong card who does not like it?
Because it was banned as early as 2007 and has not been reproduced since, the effect text on the katu remains the same. The fusion deck in the effect text, which is what we now call an extra deck. Therefore, the effect of this card is also very simple to understand, that is, 1 monster on the sacrificial field, and 1 fusion monster of the same level as the sacrificial monster is summoned from the extra deck. This summon is not a fusion summon, so the summoned monster does not appear in a regular way.
This card was first restricted in September 2005, and in the same issue of the card table, there were also Yellow Spring Frog and Scapegoat, and the additional deck was restricted to only 1 card, that is, the 1-star fusion monster Thousand Eyes Sacrifice God. So it's easy to see that the card was played primarily at the time: through the 1-star monsters of the Yellow Spring Frog and the Scapegoat, they were directly transformed into the Thousand Eyes God with a sudden mutation. The little monster suddenly turns into a super big brother, which is desperate!
The popular playing style in the arena that year also had a "level limit" tactic, which restricted the opponent's deck by restricting cards such as area B and super gravity nets that had the offensive effect of restricting high-level monsters, and using low-star powerful effect monsters such as injecting angel Lily. Sudden mutations from extra decks special summoning thousand-eyed gods are also one of the play styles that fit this tactic very well.
In the March 2007 table, the sudden mutation suddenly changed from a long-term restriction to a quasi-restriction, and 2 cards can be placed in the deck. There are 2 reasons for this, 1 is because the Thousand Eyes Sacrifice God has been banned, and 2 is the 2 cards that are the core of the level limit tactics, and the level limit B region and the super gravity net are designated as limit cards. Suddenly the mutation lost the big brother of the Thousand Eyes Sacrifice God, and naturally there was no threat. That's probably what K-society thought at the time.
But K soon realized it was wrong. Because even if you lose the big brother of the Thousand Eyes God, there is still a 7-star super big brother in the fusion deck, that is, the ultimate warrior of the alien. Players only need to obtain the super big brother of the alien ultimate warrior by summoning a level 7 variable machine beast gunner dragon at the cost of halving the attack, and then suddenly muting the gunner dragon.
At the same time, because of the advent of the homology era, players can adjust the level of monsters on the field through homophonic summoning, which is undoubtedly a very good thing for the launch of sudden mutations. Because this means that, with the exception of some fusion monsters that can only be summoned in a specific way, players can now pull any fusion monster out of the extra deck through sudden mutations. This subtle chemical reaction should have been expected by the K Society, but the actual development has obviously greatly exceeded the K Society's expectations.
Therefore, the next forbidden card table after the sudden mutation slowed down to a quasi-limit, that is, in September 2007, the sudden mutation was sent directly by the K Society into the small black house. This operation also makes it necessary to send the sudden mutation of the hand card and the 1 elemental hero blister on the field to the graveyard, and the new blister of the elemental hero that can be specially summoned becomes a waste card in the game king card pool.