Callaphe's power is equal to your devotion to blue. (Each in the mana costs of permanents you control counts toward your devotion to blue.)
Creatures and enchantments you control have "Spells your opponents cast that target this permanent cost more to cast."
(24/01/2020)
Mana symbols in the text boxes of permanents you control don’t count toward your devotion to any color.
(24/01/2020)
Callaphe’s last ability gives only one instance of the ability to creatures you control that are also enchantments.
(24/01/2020)
The ability that defines Callaphe’s power works in all zones, not just the battlefield.
(24/01/2020)
If you put an Aura on an opponent’s permanent, you still control the Aura, and mana symbols in its mana cost count towards your devotion.
(24/01/2020)
Hybrid mana symbols, monocolored hybrid mana symbols, and Phyrexian mana symbols do count toward your devotion to their color(s).
(24/01/2020)
If an activated ability or triggered ability has an effect that depends on your devotion to a color, you count the number of mana symbols of that color among the mana costs of permanents you control as the ability resolves. The permanent with that ability will be counted if it’s still on the battlefield at that time.
(24/01/2020)
Callaphe’s last ability applies to itself as well as other creatures and enchantments you control.
(24/01/2020)
Colorless and generic mana symbols (, , , , , and so on) in mana costs of permanents you control don’t count toward your devotion to any color.
(24/01/2020)
An opponent’s spell that targets a single creature or enchantment you control more than once costs only more to cast. An opponent’s spell that targets multiple creatures and/or enchantments you control costs more for each of them.
