Out Of My League
As discussed in the main guide, Path of Exile runs on a system of periodic Challenge Leagues, each lasting around three months. Each league adds some new mechanic: the Torment League, for example, added spirits that would empower enemies (the Tormented Spirits we introduced way back in Act 2), while the Bestiary League added capturable wild beasts that could be used for crafting (a more complex version of Einhar's current mechanics).
What happens after these leagues, however, has varied throughout PoE's history. Some leagues (like Torment) were added as mechanics to the core game. Others, like Legacy, were almost entirely removed after they ended. Many ended up in between, with the mechanics accessible but not nearly as present as they were during their parent league.
Leagues are usually launched alongside major content updates, which typically introduce a variety of new Unique items. Some of those items (but not all of them) are League-specific, meaning that they can only drop in a zone associated with the parent League. For example, the extremely sought-after Headhunter unique belt can only drop in zones associated with the Nemesis league.
The fate of these items after the end of their parent leagues has varied. In general, League specific uniques saw one of four possible fates after the end of their parent league:
- Added to the core game as normal drops.
- Added to the core game along with a league mechanic that dropped them. For example, Breaches were once a league mechanic, and Breaches maintained the same special drops they had during Breach League. Strictly speaking, these aren't League-exclusive uniques, they just drop from League content, but I list them here for clarity.
- Retained, but only dropped in zones explicitly associated with their parent league. For example, although the Nemesis League's core mechanic (special Nemesis modifiers on rare monsters) was added to the core game, Nemesis unique items can only drop in zones explicitly associated with the Nemesis league (usually via Zana's map device; see below).
- Generally unavailable, usually because their core league mechanic was retired and not added to Zana's map device.
Note that League-specific uniques usually cannot be the result of an Orb of Chance upgrade except in zones associated with the appropriate League.
Unfortunately, these items are not specially tagged in any way, although most Loot Filters do their best to recognize them and alert you that you've found something of value. You'll have to look up the status of whatever Unique you seek separately.
Zana's Map Mods
When you open a Map using Zana's map device, you'll have your choice of several options. Some of these will apply past League mechanics to your maps. These applications have two effects: one, they'll cause some version of that League's mechanics to appear in the opened map, but more importantly, they apply the appropriate League tag to the opened map. As a result, a Zana-opened map associated with a past league does allow you to use an Orb of Chance to acquire certain Unique items, and enables league-specific items to drop in the zone.
Each league offers a rotating selection of past Leagues on the Map Device. Not every past League is available, and when a past League is not in Zana's rotation, it becomes impossible to use an Orb of Chance to pursue that League's unique items. It is still possible to acquire them with a particular Divination Card set or sometimes via other means, but this is exceptionally rare and the associated items should be expected to be extraordinarily expensive.