Chasm of Spikes Normal Trap Card (This card is always treated as a “Trap Hole” card.) (1) When an opponent’s monster that was Normal or Special Summoned this turn declares an attack: Destroy that attacking monster, and if you do, inflict damage to your opponent equal to half its original ATK.
(For the record, the Japanese lore does not actually list this archetype clause. It has “Trap Hole” in its Japanese name instead. Same thing basically. However, it was consistently called “Chasm of Spikes” in the English versions of the anime and manga, so there you go.)