Bounties are located at the top right, 4th over from the right. These provide various buffs such as loot drop, monster essence, experience, gold drop, etc. These last for 2 hours, and you can either roll for the monster you are looking for with Bounty Cards or choose the select option.

You start off with 1 slot unlocked. Each additional slot is 150 Bounty Cards and is a 1 time cost. Utilizing this system is very important for increasing experience or loot drops.