What do the levelling stats do?

Each point in a stat adds two fixed attribute bonuses: Constitution gives health and armor toughness, Strength attack damage and armor shred, Agility speed and arrow damage, Intelligence spell power and mana, Luckiness luck and experience, and Focus mana and mana regeneration. Each stat goes up to 30, and points can be moved between stats at any time on the Levelling screen.

See Stats for the exact numbers.