A League Of Our Own
(If you are playing on the permanent Standard League, you can skip this page.)
If you've followed my recommendation, your character has been created in the current league - as of this writing, Blight (which started in early September 2019 and should last until December 2019 or so).
This page is about the mechanics of the Blight League, and will update with the release of future leagues. Previous league information can be found in the Mechanics Reference under Past Leagues.
Cassia & the Mycelium
Throughout your travels, you'll frequently encounter Sister Cassia, an NPC associated with the Blight league. Each time you find her, you'll be able to do a single encounter with the fungal Mycelium creeping across Wraeclast.
Mycelium encounters are essentially tower defense games, where you try to protect a central Pump from waves of incoming enemies that follow preset paths. Interacting with the Pump will begin an encounter.
Enemies spawn from Cysts (marked on the minimap in yellow) and follow the black Mycelium trails towards the pump. As soon as the encounter begins, you'll see a selection of available Tower locations marked by hammers, as seen in the screenshot above. You build and upgrade towers with an unnamed currency (displayed at the bottom next to an identical hammer icon). This currency is per-encounter; it doesn't preserve between them. Clicking on a tower brings up its construction menu, offering several possible tower types with different effects. For example, a Chilling tower slows enemies near it, while a Fireball tower deals higher damage.
Once you've placed towers, enemies will begin to spawn and make their way towards the Pump. Fight alongside your towers to stop them. When enemies reach the Pump, they deal damage to its durability (shown as the blue bar at the bottom of the screen); if you run out of durability, your attempt at that Mycelium encounter is over. For each enemy you kill, you'll get additional 'hammer points' to build new towers.
Occasionally, new Cysts may spawn mid-encounter, creating new paths to the Pump. Be ready to react accordingly!
If you successfully fight off the waves of enemies, you'll disable each Cyst in turn (shown by markers just above the durability bar; they're empty in the screenshot above). After the encounter, you can loot them for various rewards.
Oils & Anointing
Blight introduces a new item type: Oils. Oils are used in different mixes to add effects to Rings, Amulets, and a few special Unique items. Visit Cassia to use Oils on items.
Two oils, applied to a Ring, grants that ring a special effect that boosts your towers during Blight encounters. You can see what effect will be applied by placing a ring and the appropriate oils into the Anointing window.
Anointing Amulets or the special Blight unique items works differently. Anointed Amulets grant one Notable Passive from the Passive Tree, without that Passive needing to be connected to your tree proper. This allows for new combinations that wouldn't previously have been possible due to the high cost of traveling across the tree. Each Notable Passive on the Passive tree displays the Oils needed to Anoint it, as seen below for the notable Blood Siphon.
In addition, there are several new Notable Passives that can be acquired through Anointing that do not appear on the regular Passive Tree.
Rarely, you'll find endgame Map items that have been corrupted by the Blight. These maps lose all their initial inhabitants, and instead harbor giant, intricate Mycelium networks that serve as Blight's endgame encounters. Their mechanics are otherwise similar to normal Mycelium encounters - they're just bigger, badder, and drop more loot.