Just like the title says: If I have one garrison invasion quest available, can I get another one (and choose which one to start) or do I have to complete it first in order to get another one?
Yes, you can have multiple open invasions. (And you can choose which one / in which order you want to do them.)
But every tuesday / wednesday with the weekly reset all open invasions disappear.
Yes, you may have multiple invasion quests available at the same time. Raidri's answer is incorrect in that if you have open invasion quests, they will not disappear at the weekly reset.
I can confirm that it lasts through a reset. I had 2 stacked at one point.
There was a bug at launch that would reset all progress towards all invasion quests at the weekly reset, which meant they disappeared, but they fixed that bug with the December 2nd hotfix, and your invasion progress carries over, with your currently available invasion quests staying intact.
- Garrison Invasions
- Corrected an issue that was causing progress towards a Garrison invasion to reset each week.