Rituel
Piochez trois cartes.
Inflexible — Si au moins trois manas bleus ont été dépensés pour lancer ce sort, regard 3.
If an effect allows you to cast a spell without paying its mana cost, you can't choose to cast it and pay unless another rule or effect allows you to cast that spell for a cost. Similarly, you can't waive a cost reduction unless that effect says you may.