Advanced format ruling
Chthonian Blast
Card effect (current official text)When a face-up monster you control is destroyed and sent to the Graveyard: Destroy the 1 face-up monster on the field that has the lowest ATK (your choice, if tied), and if you do, inflict damage to both players equal to half of that monster's ATK.
Current rulings for this card are maintained by Konami.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Advanced forum — sourced change requests get reviewed.