Maybe catching a pretty damsel?  Just hypothesizing.

JCD

A net is used to catch monsters instead of killing them (monstology).  You can then take them to Thord-Artin to repopulate them.  You will not be able to do this, however, until you have killed 100 of the occupying army on Thord-Artin, which will not be possible until you are at least level 24, more likely around 30.  You will also need a boat.

Speaking of boats, you also need nets when you purchase or upgrade your boat.

Search the forum for more info on these topics, or check out larkinorguide.com (tools and articles, monstology)

Subprime

Correction.  While it is possible to kill Blue Cityguards (part of the occupying army on Thord-Artin) at level 24, you will not be able to kill 100 of them at level 24 because the combined experience from killing them would make you level 25.  Killing 100 at any level below 29 is extremely tedious, and I would not recommend it.

Subprime

A net is used to surf the web, of course! :)