You can receive IOUs by giving  Galash the Merchant or  Squire Voldemar certain resources.  

IMPORTANT: The resources can be handed in throughout the entire event, including Return of The Merchants phase.

You can find more info about the resources in the table below.

Resource	Note	IOUs		Resource	Note	IOUs
1	Can be exchanged 1 time a day	150		1	Can be exchanged 1 time a day	100
1	Can be exchanged 1 time a day	50		1	Can be exchanged 1 time a day	25
2	-	50		3	-	30
3	-	75		3	-	30
1	-	25		10	-	20
1	-	20		3	-	45
1	-	20		5	-	15
5	-	100		5	-	15
5	-	100		1	Only one, based on your choice	20
5	-	150		1		20
5	-	25		1	Only one, based on your choice	75
5	-	35		1		150
	-	30		1		300
3	-	60		5	-	25
3	-	30		1	-	150
3	-	30		1	-	150
3	-	30		1	-	150
3	-	40		2	-	50
3	-	350		1	Can be exchanged 1 time a day	2000

You can also hand in resources from the Rahdarian deserts every 12 hours:

For every 50 resources turned in, you will receive: 50x Inspiration of Datkhars and 250x IOUs.

NOTE: The progression counts resources turned in, not trades. It means if you make one trade using 10 resources, the progression bar will raise by 10, not 1.

When the travellers are back you will be able to exchange IOUs for the goods they will have brought with them. You haven't seen goods like that before!

Till the end of 3rd stage of the event at  Galash the Merchant and  Squire Voldemar, for IOUs you will be able to purchase various goods, which will be available only during that time.