Brighthearth Banneret — ruling 1

The effect reduces the total cost of the spell, regardless of whether you chose to pay additional or alternative costs. For example, if you cast a Rogue spell by paying its prowl cost, Frogtosser Banneret causes that spell to cost {1} less.

Brighthearth Banneret — ruling 2

A spell you cast that’s both creature types costs {1} less to cast, not {2} less.

Brighthearth Banneret — ruling 3

When you cast an Elemental spell by paying its evoke cost, this effect reduces the cost to cast that spell by {1}.

Brighthearth Banneret : règles, fonctionnement et interactions (MTG)

Brighthearth Banneret is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Elemental spells and Warrior spells you cast cost less to cast. Reinforce 1— (, Discard this card: Put a +1/+1 counter on target creature.)

How it works : Brighthearth Banneret

Original English text — Wizards of the Coast / Scryfall

#1April 1, 2008· Wizards of the Coast
The effect reduces the total cost of the spell, regardless of whether you chose to pay additional or alternative costs. For example, if you cast a Rogue spell by paying its prowl cost, Frogtosser Banneret causes that spell to cost less.
No other card is named in this ruling.
#2April 1, 2008· Wizards of the Coast
A spell you cast that’s both creature types costs less to cast, not less.
No other card is named in this ruling.
#3April 1, 2008· Wizards of the Coast
When you cast an Elemental spell by paying its evoke cost, this effect reduces the cost to cast that spell by .
No other card is named in this ruling.