Path of Exile’s September expansion is called Blight, and it adds a new tower defence-style mode to the free-to-play hack ‘n slasher. The update also makes some changes to several classes and incorporates two old leagues into Path of Exile’s core game.
Your task in Blight is to help Sister Cassia stop the spread of the Blight, a plant-like organism that controls monsters’ minds. When they’re possessed, the monsters become tougher, but they mindlessly follow tendrils created by Fungal Growths. To stop them, you need to build defensive structures that exploit the creatures’ specific weaknesses, efficiently using both space and resources to survive.
Each time you successfully defend a tendril, which is effectively a lane, you’ll get acces to a chest full of rewards. Sister Cassia can also use oils dropped during battle to enchant items as you play.
In terms of defensive structures, Blight gives you a wide arsenal to bring to bear. There are towers that cause chill, shock, stun, burn, petrify, and debilitate. Some towers stun and others empower your characters.
Original source: https://www.pcgamesn.com/path-of-exile/blight-launch