Expansive Mind is racial talent possessed by all Gnomes, increasing their Intellect by 5%.
Note: The information above is no longer accurate. This ability now increases your mana pool by 5%. This is only useful for abilities directly connecting to your number of mana points, like Mana Shield; spell costs scale with mana.
Each point of intellect increases your mana pool by 15.
You need ~166 intellect to increase your chance to critically hit with spells by 1% at level 80.