is one of the six core character attributes
Toughness grants additional Health and Defense vs DoTs (Damage over Time effects).
Each point in Toughness grants an additional 1 point to Health, up to 250 Toughness.
Health = Base health + Toughness
Above 250 Toughness, the formula changes:
Health = Base health + 250 + (Toughness / 4)
See the below table for example values:
Therefore, it is recommended that you achieve at least >250 Toughness, but then you may want to allocate your other points elsewhere.