Advanced format ruling
Mysterious Triangle
Card effect (current official text)Destroy 1 monster on the field with an A-Counter. Then, you can Special Summon 1 Level 4 "Alien" monster from your Deck. Destroy it during the End Phase.
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.