If you are in RoK doing the quest where you get a disguise to go into the den of the widow mistress to find a case that was lost, Take the quest but dont finish it. If you complete the quest then you lose the arachnid disguise.

Here's why
There are alot of rocks in there to mine and with that disguise you have 1 hour of no aggro to mine away and get them rares. They are selling for 2 or 3 plat currently on the broker and it is right there when you first get into the zone. No running around and wasting time. watch the timer on your disguise and find a safe spot to recast it before it wears off. You can make about 30 plat from selling rares from there in 1 day.

For you pvps. You can run from the enemy and quickly throw on the disguise and run in there if you are being chased. Watch the other noobs get pwned by spiders because they are aggro to them and not you.

The disguise now disappears when attempting to mine, making this not more useful then normal invis ability.