Adamant

Adamant is an ability word introduced in Throne of Eldraine for spells of the five courts that make up "the Realm".

Description
Spells with Adamant have additional or alternative effects if you cast the spell with three or more mana of one color. The text is different on each color of spell, as colored spells specify the spell's color whereas the two artifact spells outline that any color can be used.

There are three cycles of Adamant spells printed (a cycle of common Knights, and two cycles of instant or sorcery spells, one common and one uncommon), plus two artifact creatures and one unworded super-Adamant spell (Sundering Stroke) that takes effect when paying seven red mana.

Rulings

 * If an instant or sorcery spell has an adamant ability, you perform the spell's instructions in order. You don't perform the adamant instruction before the spell resolves or before any other effects printed above it.
 * If an effect allows you to cast a spell without paying its mana cost, you can't choose to cast it and pay unless another rule or effect allows you to cast that spell for a cost. Similarly, you can't waive a cost reduction unless that effect says you may.
 * Adamant effects check what mana was actually spent to cast a spell. If an effect allows you to spend mana "as though it were mana" of any color or type, that allows you to spend mana you couldn't otherwise spend, but it doesn't change what mana you spent to cast the spell.
 * If you copy a spell that has an adamant ability, no mana was spent to cast the copy at all, so that ability won't apply.