Hardened Berserker — ruling 1

Hardened Berserker can’t reduce the colored mana requirement of a spell you cast.

Hardened Berserker — ruling 2

If there are any additional costs to cast a spell, apply those before applying Hardened Berserker and any other cost reductions.

Hardened Berserker — ruling 3

The ability can apply to alternative costs to cast a spell.

Hardened Berserker : règles, fonctionnement et interactions (MTG)

Hardened Berserker 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

Whenever this creature attacks, the next spell you cast this turn costs less to cast.

How it works : Hardened Berserker

Original English text — Wizards of the Coast / Scryfall

#1February 25, 2015· Wizards of the Coast
Hardened Berserker can’t reduce the colored mana requirement of a spell you cast.
No other card is named in this ruling.
#2February 25, 2015· Wizards of the Coast
If there are any additional costs to cast a spell, apply those before applying Hardened Berserker and any other cost reductions.
No other card is named in this ruling.
#3February 25, 2015· Wizards of the Coast
The ability can apply to alternative costs to cast a spell.
No other card is named in this ruling.