The free to play Action RPG by Grinding Gear Games, Path of Exile is most often compared to the Diablo series, and benefited on launch from the situation (read: disaster, mess, and however else you want to describe it) around Diablo 3's launch. It leaned into that further with being a free to play Action RPG, that unlike the major Blizzard release lacked any elements of pay-to-win, something that the title has long been lauded for, along with its mechanics.
Here's a description from the steam store page:
You are an Exile, struggling to survive on the dark continent of Wraeclast, as you fight to earn power that will allow you to exact your revenge against those who wronged you. Created by hardcore gamers, Path of Exile is an online Action RPG set in a dark fantasy world. With a focus on visceral action combat, powerful items and deep character customization, Path of Exile is completely free and will never be pay-to-win.
- Freedom. Power. Revenge. Banished for your misdeeds to the dark, brutal world of Wraeclast, you play as the Duelist, Witch, Ranger, Templar, Marauder, Shadow or the Scion class. From forsaken shores through to the ruined city of Sarn, explore Wraeclast and uncover the ancient secrets waiting for you.
- Unlimited Character Customization Create and customize hundreds of unique skill combinations from tradable itemized gems and our gigantic passive skill tree. Combine skill gems, support gems and trigger gems to create your own unique combination of power, defense and destruction.
- Deadly Missions The Forsaken Masters each have their own style of mission and each of these missions has many variations. As you explore deeper into Wraeclast, the pool of available variations increases to challenge you in new ways. All of the Missions and their variations can occur anywhere in the game, including within end-game Maps.