Power

Any spell tooltip with orange numbers in-game is scaled from your Power.

If a spell says it does 1238 damage in orange The ratio would be 1283/power = 1.522. So any time you cast that spell the real damage dealt is 1.522 * current power

There are multiplicative and additive power boosts :

Ex: Gospel of Onslaught gives a multiplicative power boost

Ex: Enrage Increases Power by 144