Flashback

Flashback is a special race event that GGG occasionally held.

Flashback were held during Warbands, Perandus, Bestiary, Incursion, Synthesis league and Heist league, etc.

It usually not a void league parallel and parented to the temporary challenge leagues at that time.

Usually the event would award the winner with unique item that named after Demigod. Such as (Heist),  (Synthesis),  (Perandus, Bestiary, Incursion), etc.

Modifiers
Each areas of the league have a few random modifiers that resembled to past league mechanics. Below is the list of possible pool of such mods, despite GGG reserved the rights to disable individual mods (for example, Warbands was not in the actual pool since 2016    ):

Note that these area mod does not mean the area has the league flag. Unique item that requires a specific league flag cannot drop this way. Such as (requires Nemesis league flag) and  (requires Ambush or Invasion league flag), etc.

However, since most post-3.0 league unique items are tied to the mechanics (e.g. Abyss/Breach/Warbands monster/bosses, Legion/Blight encounter, tied to Beachhead Maps, tied to Perandus chest, etc.) instead of rely on league flag, those unique can still be obtained from Flashback league. Moreover, Zana use the same crafted modifiers that available to all leagues of that patch/expansion, which Zana crafted modifiers can add league flag to the map area. Zana crafted map mod has a hidden property  which is not found in the relevant flashback mod.