Converge

Converge is an ability word introduced in Battle for Zendikar, which highlights spells whose effects depend on the number of colors of mana you spend to cast them.

The key difference between the similar Sunburst and Converge is that the first is a keyword with a static ability which is only permitted on creatures and artifacts while Converge is an ability word which can go on nonpermanent spells.

Converge also appeared in Commander 2016 (Crystalline Crawler) and in a cycle in Modern Horizons 2.

Rulings

 * You are limited to the mana cost of each spell. You can't use more (colorless) mana.
 * If a spell with converge on the stack is copied, it's just created on the stack. No mana was spent to cast the copy, so zero colors of mana were spent to cast it.