Endless tower is a 100 floor tower where you kill numerous MINI/MVP's along the way. The entire group receives drops so you're not fighting for the kill. This is some of the easiest instanced content the game that new players should be getting into as soon as possible.
Once you hit base level 50 this content will automatically unlock in your instance menu.
Location of Endless Tower in the Instance Menu
Kill all monsters and climb the tower, it's that simple. Every time a floor is cleared everyone in the group will receive loot that would drop from each monster on that floor. Every couple floors you'll encounter some MINI(s), and every 10th floor you'll always encounter some MVP(s). As you climb higher up more of these will spawn.
If you're new you want to get into a group for this every week. While you won't be able to run this far by yourself for a long time, other established players should blaze through this instance.
Photo's can be taken of monsters here, including MINI and MVP. This is the only instance that you can do this in and will fill up your adventure handbook quickly. I strongly advise you to take advantage of this since MVP monsters are hard to find in the wild since there is competition for their drops.
I cannot recommend this enough for a new player since it’s extremely easy to be carried through this. There are plenty of people who need to run this every week so don’t be afraid to ask for help!