Addendum

Addendum is an ability word introduced in Ravnica Allegiance for the Azorius Senate. 
==Description==
Spells with Addendum have additional or alternative effects if you cast the spell during your main phase. Addendum is found mostly on instants. The exception is <c>Sentinel's Mark</c>, which is an enchantment with flash.
Addendum designs were made in two forms: instants with main phase upside, and functional sorceries with weaker instant versions.
===History===
A similar cycle of "main phase matters" instants had previously been featured in Time Spiral. These were designed without the difference in mind, as they have a numerical value (one more card, one more damage) increased if cast in the main phase. A callback to this, , plays closer to Addendum. The cycle of instants with Landfall from Worldwake have a similar function, though not literally; fetchlands had already been printed, allowing out-of-turn landfall, but as a general rule, they were stronger during their owners' turn as that is the time most likely when they would have had a land enter. 
Addendum appeared as a one-off in the Streets of New Capenna Commander decks. is unique amongst Addendum spells as the main phase effect occurs before the standard effect.
==Examples==
==Rulings==
*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.
==References==