Emergency Powers
Instant
Each player shuffles their hand and graveyard into their library, then draws seven cards. Exile Emergency Powers.
Addendum — If you cast this spell during your main phase, you may put a permanent card with converted mana cost 7 or less from your hand onto the battlefield.
Illustrated by
Ravnica Allegiance#169MythicEnglishLegality
Rulings
If a card in your hand has 
in its mana cost, X is considered to be 0.
Addendum abilities of instant spells apply while the spell is resolving, not immediately after casting it. If the spell is countered, you don’t get the addendum bonus. For example, if you cast Sphinx’s Insight during your main phase, you gain 2 life during its resolution, after you draw two cards.
If a spell with an addendum ability is copied, the copy won’t give you the addendum bonus. This is because the copy wasn’t cast at all.