Mana from Curious Homunculus's first ability can be spent to cast a spell that has generic mana in its additional cost, such as Borrowed Malevolence with both modes chosen. It can't be spent to pay costs during a spell's resolution, such as the cost Convolute prompts a player to pay.
2016-07-13
wotc
If you don't have enough instant and/or sorcery cards in your graveyard as your upkeep begins, Curious Homunculus's last ability doesn't trigger. If you don't have enough as the ability resolves, the ability has no effect.
2016-07-13
wotc
If you activate Curious Homunculus's mana ability in response to its triggered ability, you can spend that mana to cast an instant spell during your upkeep after it has transformed into Voracious Reader. If you don't spend the mana, it will be lost before your draw step begins; you can't use it to cast the card you draw or to cast a sorcery.
2016-07-13
wotc
If an instant or sorcery spell has {X} in its mana cost, choose the value for X first, and then reduce the cost by {1}. For example, Dark Salvation with X chosen as 2 costs {3}{B} to cast if you control Voracious Reader.
2016-07-13
wotc
Abilities that reduce the cost of a spell apply after abilities that raise them. For example, Borrowed Malevolence with both modes chosen costs {1}{B} to cast if you control Voracious Reader.
Format Legality
Standard
Not Legal
Future
Not Legal
Historic
Legal
Timeless
Legal
Gladiator
Legal
Pioneer
Legal
Modern
Legal
Legacy
Legal
Pauper
Not Legal
Vintage
Legal
Penny
Not Legal
Commander
Legal
Oathbreaker
Legal
Standardbrawl
Not Legal
Brawl
Legal
Alchemy
Not Legal
Paupercommander
Not Legal
Duel
Legal
Oldschool
Not Legal
Premodern
Not Legal
Predh
Not Legal
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