Path of Exile: Sentinel is an expansion to the fantasy action RPG Path of Exile, which adds new locations and bosses to the game. The new league introduces Sentinels—special constructs that enhance enemies, thereby increasing the level of rewards. There are three types of Sentinels: Stalkers (sequentially empower a moderate number of enemies as they are encountered), Pandemonium (simultaneously empower a large crowd of monsters in one swift burst), and Apex Sentinels (empower only rare or unique enemies). All constructs have a certain charge. Over time, it depletes, but players can combine them into a new Sentinel that inherits the properties of its predecessors.
Also in "Sentinel" a new currency has appeared—recombinators. They allow combining two pieces of equipment of the same class to obtain a new item with unique properties. The result is unpredictable, but with some luck, it can be a very powerful item. In addition, 20 new keystone skills have appeared on the Atlas tree. Six of them create uber versions of the pinnacle bosses: Venarius, Sirus, The Maven, The Searing Exarch, The Eater of Worlds, The Shaper, and Uber Elder.
The expansion requires the original version of Path of Exile.