For those who are new, what is a Tower Event?
A tower event is an event with 50/100 floors for each lap. There is a boss fight every 10 floors. In the normal fights, you are generally allowed 3 allied units and only 1 of your own unit. The deploy layout somewhat resembles that when you attack other players and fight their defense.
Once you have completed all 50/100 floors, you complete one lap and start over again from floor one. For each lap completed, you get a prize, generally a monster unit card. You also tend to get a prize for every tenth floor (i.e 10th, 20th, 30th) completed.
Tower events tend to be time consuming
but it is less "pay to win." (not anymore due to the BT 8* reward)
They also tend to be great for beginners because you can easily get a 5* monster unit which tends to be recruitable (and thus you get a 5* unit after recruiting it at the next recruitment event)
100 floors is 20 hours worth of cooldowns at three attempts per boss.
Spread that over a week and it's less than three hours a day!