Every other timing rule for casting spells still applies: If the mayhem card is an instant, you can cast it any time you have priority that turn, but if it's a creature you can only cast it at sorcery speed (unless another effect gives it flash)
General japanese , question , modern 46 1964 February 20, 2023 QotD: What are some of the most extreme examples of quality difference between Japanese and English cards
If you activate this spell, you cannot conduct your Battle Phase that turn
When this card declares an attack on an opponent's monster: You can target the attack target
You can only use each of the following effects of "Kashtira Unicorn" once per turn
As a result, there are currently no archetype condition or archetype-exclusion condition associated with "Chaos" monsters even if it would otherwise result in one