Chthonian Blast is a Normal Trap Card.
Trap Cards are normally Set first and can be activated on a later turn, often in response to an action.
On the current TCG and OCG Forbidden & Limited lists tracked here, Chthonian Blast is Unlimited.
YGOPRODeck lists Chthonian Blast for these formats: Duel Links, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of Chthonian Blast appears in Dark Revelation Volume 4 (DR04-EN110) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Chthonian Blast is about $0.08 on Cardmarket (prices change frequently).
