Frightful Delusion — ruling 1

You must target a spell in order to cast Frightful Delusion. You can’t cast it without a legal target just to make a player discard a card.

Frightful Delusion — ruling 2

The player discards a card even if they pay {1}.

Frightful Delusion : règles, fonctionnement et interactions (MTG)

Frightful Delusion is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Counter target spell unless its controller pays . That player discards a card.

How it works : Frightful Delusion

Original English text — Wizards of the Coast / Scryfall

#1September 22, 2011· Wizards of the Coast
You must target a spell in order to cast Frightful Delusion. You can’t cast it without a legal target just to make a player discard a card.
No other card is named in this ruling.
#2September 22, 2011· Wizards of the Coast
The player discards a card even if they pay .
No other card is named in this ruling.