The new atlas shows symbols on maps where a master mission will be available: And while I recognize the symbol for bestiary, it would be nice to have a resource to look up the meaning of each symbol to be sure what mission is available there. The path of exile gamepedia on the atlas doesn't include this information.
Going from left to right:
Dark blue "gear": Delve (Niko). Map contains 3 Sulphite nodes.
Blue fleur-de-lis: This indicator was teased but is not used in-game. The symbol is identical to the symbol used for the player hideout, and was speculated to be related to Helena.
Red bow and skull: Bestiary (Einhar). Map contains several yellow beasts and at least one red beast.
Yellow wing and claw: Syndicate (Jun). Map contains up to three Immortal Syndicate encounters.
Two tone green/red "V" symbols: Incursion (Alva). Map contains up to three Incursion altars.
Bright blue circle with bronze gears: Atlas (Zana). Zana is present in the map and will offer a selection of missions.