Mercenary: Flash of Blades

 is a challenge in Risk of Rain 2. It is completed as by using 20 abilities in 10 seconds.

Tips

 * This can be achieved without a single item and when using the default loadout. While fighting a little packed group of enemies, holding left click to attack continuously and applying the Exposed status to as many enemies as possible can allow to recharge your dash quickly enough to reach the number of attacks required.
 * and allow you to stack uses of secondary and utility attacks. Having enough will make this challenge trivial.
 * can also allow you to spam attacks for several seconds after killing an elite.
 * As with most of the challenges, the makes it easy to get the items you need.
 * It is also possible to complete the challenge between runs if you continuously restart the run after spamming as many abilities due to the challenge counting in game time and not resetting the counter after each run