Guide to Guild Daily Quests in ESO

To participate in Mages Guild daily quests, you must first be a member of the Mages Guild in ESO. You can join the Mages Guild by visiting the Mages Guild Hall in Glenumbra, Auridon or Stonefalls and speaking to the NPC just inside the main door. Check out this guide for more information about the location. 
Once you have joined the Mages Guild, you will be able to obtain the daily quests by visiting the Mages Guild Hall in any of the main alliance hub cities: Wayrest in Stormhaven, Elden Root in Grahtwood (behind the throne room of the Upper Level of the Elden Root tree) or Mournhold in Deshaan. Speak to the NPC called Alvur Baren, who will task you with recovering a Sheogorath artefact from a randomly selected base-game public dungeon. You will need to travel to the specified public dungeon, retrieve the artefact at the quest marker and then return to Alvur Baren to hand in the quest and recieve your reward. 

Mad God's Coffer in ESOThe reward for this daily quest is the Mages Guild Merits container, which generally contains a glyph, some ornate gear to sell at a vendor, and might also contain a page from the Draugr style motif or the associated crafting material. You will also receive 10 Mages Guild XP.
Mages Guild location in WayrestMages Guild location in MournholdLocation of door to Upper Level in Elden Root