This question is about the Supernatural Fury feature of the Path of the Sacred Kin from Xanathar's Lost Notes to Everything Else (a third-party book which can be found on dmsguild.com).
At 3rd level, you can focus on the magic in your blood, allowing you to concentrate your rage into the ancient magic of your bloodline and enter a Supernatural Fury. You gain the ability to cast and concentrate on spells, even while raging, at the expense of your physical resistances.
When you enter your Supernatural Fury and you aren’t wearing heavy armor, the following benefits replace the benefits of the Rage feature:
- You gain a bonus to your AC equal to your Strength modifier (minimum of +1).
- You have advantage on Constitution checks and saving throws made to maintain concentration on a spell.
- You have resistance to magical damage and are immune to the damage type you chose from your Ancestral Origin.
Your Supernatural Fury lasts for 1 minute. It ends early if you're knocked unconscious or if your turn ends and you haven’t attacked a hostile creature, cast a spell, or taken damage since your last turn. You can end your Supernatural Fury on your turn as a bonus action.
Does this mean the Sacred Kin barbarian can choose between entering a "regular" rage and a Supernatural Fury? Or can he (from Level 3 on) only gain the benefits from Supernatural Fury, because it completely replaces the "old" rage he used on Level 1 and 2?