Delirium is the name of the upcoming Path of Exile league. In the new league, areas will contain Mirrors of Delirium that spawn enemies and make existing enemies more difficult when you pass through them. It seems to be similar to a breach and will include a loot streak mechanic.
Once the Mirror of Delirium is activated, current mobs become stronger and new Delirium specific mobs start to spawn. Other encounters still function, such as opening a breach, while Mirror of Delirium is active. The Delirium effect grows outward in a circular radius.
PoE Delirium Release Date
PoE Delirium is set to release on March 13th, 2020 UTC. The official Path of Exile: Delirium trailer with gameplay and commentary can be viewed here:
PoE Delirium League Currency
Orbs of Delirium will be added in the upcoming league. These orbs add weighted delirium map modifiers and 20% delirium encounter effect across the map. You can apply up to five of these orbs per map to get the full delirium effect. This cannot be applied to unique maps.
A new jewel type called Cluster Jewels will also be added to the game. These jewels add new passive clusters that can include another socket for additional chaining. Jewel passives will mostly be free to respect. Cluster Jewel enchantments will limit what notables are rolled and cannot be altered.
New Skill Gems
Blade Blast – detonate blades that are now left behind by Ethereal Knives, Blade Vortex and Bladefall for a potent combo.
Kinetic Bolt – fire a projectile from your wand that bounces back and forth, forking with each bounce. Spell damage further empowers the wand attack.
Stormbind – place storm runes on the ground that spread out as you channel. You can then channel mana into your runes, upgrading and detonating them.