Stormcatch Mentor
Creature — Otter Wizard
[[ keyword: "Haste" ]]
Prowess
Instant and sorcery spells you cast cost 
less to cast.
"Only novice mages burn their whiskers. So pay attention!"
Manuel Castañón
Bloomburrow (BLB)
• #234Rulings
The cost reduction applies only to generic mana in the total cost of instant and sorcery spells you cast.
(wotc • 2024-07-26)
To determine the total cost of a spell, start with the mana cost or alternative cost you’re paying (such as a flashback cost), add any cost increases (such as kicker costs), then apply any cost reductions (such as that of this ability). The mana value of the spell is determined by only its mana cost, no matter what the total cost to cast that spell was.
(wotc • 2024-07-26)
Rulings
The cost reduction applies only to generic mana in the total cost of instant and sorcery spells you cast.
(wotc • 2024-07-26)
To determine the total cost of a spell, start with the mana cost or alternative cost you’re paying (such as a flashback cost), add any cost increases (such as kicker costs), then apply any cost reductions (such as that of this ability). The mana value of the spell is determined by only its mana cost, no matter what the total cost to cast that spell was.
(wotc • 2024-07-26)