Arc and Crackling Lance gains Added Cold Damage equal to 20% of Mana Cost, if Mana Cost is not higher than the maximum you could spend 25% increased Cost of Arc and Crackling Lance

What this record tells you

This is a crucible tree modifier available from level 1. Its listed spawn tags determine which item families can naturally receive it.

Positive spawn weight means the modifier is eligible for that tagged item family. A zero weight blocks it for that tag. Weight is relative—not a simple percentage by itself.