Damage type of this hit is not elemental; if used against players, it takes average of resistances to mitigate ( Armor also works against it).

However, with patches, it was allowed to benefit from Physical elemental skill damage bonuses, unless another type is specifically stated.

Thorns can trigger special effects where possible, but have the zero proc coefficient.

Many items, gems ( Topaz in weapons and Boyarskys Chip ) and even one set enhance Thorns.

Note that most percentage enhancements of Thorns from items or skills are additive, stacking directly (not multiplicatively).

VoToyias Spiker and some other temporary effects are exceptions, being multiplicative to all other enhancements.

With Ancient Legendary items, these values can go up to 75504 95540.

A Topaz gem in the weapon socket can also add up to 38000 damage to Thorns.

However, a good assortment of protection can make the total damage inflicted with Thorns quite considerable, easily allowing a player with sufficient primary stat andor thorns to make monsters lose more Life per hit than the damage they successfully inflict upon the hero.

It is most effective against weak numerous attackers, especially if those are way below the character in Life and damage; on lower difficulties, one may kill most foes without as much as pressing a button.

Collecting the variety of Thorns-centered gear can turn this mechanic from defensive to offensive, so a well-armed Crusader may, if desired, make it a lethal weapon.

Considering that players generally have less Toughness than monsters, it may prove even more effective in PvP than against the minions of Hell.

D3 Dmg Calculator