Invasion league

In the Invasion, areas of Wraeclast have substantially more monster variety, so players will run into unexpected and dangerous invading monsters from other levels or acts. A unique boss monster from an invading monster type is also lurking in each level, with powerful combinations of skills to catch the player off-guard.

Description on the official Path of Exile website

The Invasion league was a four month league aimed at players who were looking for more challenging gameplay. In this league all areas had been invaded by monsters from all over Wraeclast. A unique Invasion Boss from an invading monster type was also lurking in each level. Higher difficulty levels contained expanded monster variety and invading bosses with more abilities.

It started along with the Ambush league on March 5, 2014 and lasted until July 5, 2014. At the end of the league all surviving characters and stashes were moved to the Hardcore league. Characters that died during the four months were moved to Standard league immediately.

Modifier

All areas had

Items

Invasion had nine exclusive base item types (all shared with Ambush) and three exclusive uniques (two of which were shared with Ambush).

Exclusive base item types

The following item types were introduced exclusive to Ambush and Invasion.

Exclusive uniques

The following uniques were shared between Invasion and Ambush.

These uniques were specific to Invasion, but was added as a drop to the core game at the league's end.