Arrester's Zeal
Instant
Target creature gets +2/+2 until end of turn.
Addendum — If you cast this spell during your main phase, that creature gains flying until end of turn.
Law is the light of civilization.
Izzy
The List (PLST)
• #RNA-4Rulings
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.
(wotc • 2024-01-12)
If an effect copies a spell with an addendum ability while it's on the stack, the copy wasn't cast at all, so you won't get the addendum bonus.
(wotc • 2024-01-12)
Printings
Price History (USD)
Price History (EUR)
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.
(wotc • 2024-01-12)
If an effect copies a spell with an addendum ability while it's on the stack, the copy wasn't cast at all, so you won't get the addendum bonus.
(wotc • 2024-01-12)