Shield

A shield is a temporary layer of protection that absorbs incoming damage before it touches a champion's health, usually for a few seconds. Shields come from certain abilities, items, and the Barrier summoner spell, and many block only one damage type — physical, magic, or both.

Well-timed shields counter burst damage by soaking the key spell in a combo, which is why enchanter supports built around shielding are so valuable to fragile carries. Reading when to use a shield, rather than spending it early, is what separates a strong support from an average one.