Radiant Steadfast Heart

radiant

+40 Armor
+40% Crit

Gain 10% Durability. While above 50% Health, instead gain 30% Durability.

Source

Radiant

Base item

Steadfast Heart

Radiant Steadfast Heart enables

Durability

Durability is a percentage damage reduction that cuts incoming damage.
Armor

Armor is the physical-defense stat that reduces incoming Attack Damage (AD) damage.
Crit

Crit means a unit's damage scales with crit chance and crit damage.