This guide will not attempt to describe harvesting basic resources and gold using caravans; there is already an admirably detailed guide on the subject written by Mara Zira that can be found here:  http://forum.illyriad.co.uk/step-by-step-guide-to-harvesting-resources_topic2290.html" rel="nofollow - http://forum.illyriad.co.uk/step-by-step-guide-to-harvesting-resources_topic2290.html .  Knowledge of basic gathering can be helpful background when reading this guide.

In the July 2012 release a new unit was introduced to do basic gathering:  the cotter.  Building a cotter requires the following steps:

1) Study Cotters in the Trade branch of the research tree:   http://elgea.illyriad.co.uk/#/Research/Tree/5" rel="nofollow - http://elgea.illyriad.co.uk/#/Research/Tree/5

2) Build one or more cottages for your cotter to live in.  Each cottage takes one building plot and allows you to create one cotter.  If you build cottages and cotters and then destroy some cottages, your newly homeless cotters will desert your city at their next opportunity.  Number of cottages in a city = number of cotters that can be built.

3)  Produce cotters on the trade train units screen, accessible by mousing over the gold coins and clicking on the donkey at the right:   http://elgea.illyriad.co.uk/#/Town/UnitProduction/9" rel="nofollow - http://elgea.illyriad.co.uk/#/Town/UnitProduction/9

4) Study Foraging in the trade branch of the research tree.  Study of Foraging enables your cotters to harvest Herbs, Minerals and Hides.  In order to harvest grapes, you must study Grape Picking.

5) Find and harvest resources on the world map.  The resources that can be harvested by cotters are:

Minerals 

Cotters can harvest and carry up to 100 of the item they are harvesting.  Cotters harvest at a rate of 5 resources per hour, except for human cotters, which harvest at a rate of 7 resources per hour.  

Cotters will continue harvesting until 1) they have collected 100 of a resource 2) the remaining harvestable resources on the square are exhausted, 3) they are interrupted by another cotter or harvester, either yours or another players, 4) they are recalled by messenger or 5) they are killed by a non-allied army attacking or occupying the square.  

If cotters are interrupted while harvesting, they take home the fruits of their labor rounded down to the last hour.  For example, if a dwarf cotter was harvesting a mineral patch and was interrupted after 30 minutes, it would return home with nothing.  If it was interrupted after 4 hours 45 minutes, it would return home with 20 (4 times 5) of the mineral.

More than one cotter can be sent to a square; the cotters will harvest in parallel, harvesting twice as fast if two cotters are sent, for example.

If there is more than one resource that cotters can harvest on a square, such as hides and minerals or hides and herbs, then the cotter will choose one of the resources and gather as much as possible of that resource (either the entire remaining amount or 100) and then leave.

1.  Minerals

Mineral patches are permanent; if they are exhausted they will eventually be replenished in the same location.  They tend to be found in rocky or mountainous terrain.

2.  Herbs

Herb patches will continue growing unless they are completely exhausted by a harvester.  If they are exhausted, the patch will be relocated elsewhere.  Herbs tend to be found in forest terrain.

3.  Hides

Hides are found in locations where NPC animals have been killed, either by player armies or by conflict with other animals.  Danger:  If there are live animals remaining on a square, they will kill incoming cotters or other harvesters, although once a harvester is safely on a square it will not be killed by incoming animals.

III.  Gathering Rare Herbs, Rare Minerals and Animal Parts (Including Elemental Salts)