Zana, Master Cartographer
Zana is the last of the Masters that you'll meet as part of the main story. Einhar has Beasts, Niko has Delves, Alva has Incursions, and Zana has Maps. You'll meet Zana in the Epilogue, in the restored Oriath Square. She'll ask for your help, give you your first map to run, and start a quest chain that you'll follow throughout the endgame.
The Map Device
Once you've met Zana, she'll give you access to the Map Device, an object you can place in your Hideout. It allows you to open Maps from your Hideout, which becomes your main 'town' for the endgame.
The Map Device applies modifiers to a map as you open it, rather than crafting them explicitly onto the map item itself. Applying these modifiers is moderately expensive, but can be lucrative on high-tier maps with large modifiers to Item Quantity (where they can easily pay for themselves with increased drops). Importantly, some of Zana's map modifiers count as running a map with a particular League enabled, which allows drops restricted to past leagues to appear. This is one of a very few ways to get past league-exclusive items.
You can unlock additional options at the Map Device by completing Zana's endgame quest chain.
Like the other Masters, you can encounter Zana while adventuring. This time, though, you'll encounter her within Maps, and she'll offer you a choice of several other Maps to run. Some of these maps can be rare and valuable, and there are several Unique maps that are specific to Zana herself. You'll always want to run them, at any rate, because they effectively represent free extra maps at no cost to you.