You can fight with boss every day only one time.
You cannot fight with boss even if you lose.
Any drop from boss have 3% chance, gold has 100% chance.

Bosses Name
Level
Exp
Event Points
Loot
Zabuza Defender
1-49
110.000
1
1x
Haku Defender
50-99
1 level
1
1-2x
Kimimaro Defender
100-199
1 level
2
1-5x
Orochimaru Defender
Yamato Defender
200-299
1 level
3
1-10x
Danzo Defender
Kisame Defender
300-399
1 level
4
1-10x
Hinata Defender
Neji Defender
400-499
1 level
5
1-15x
Choji Defender
Menma Defender
500-599
1 level
6
1-15x
Minato Defender
Nagato Defender
600-699
1 level
7
1-15x
Gaaara Defender
Obito Defender
700-799
1 level
8
1-25x
Shisui Defender
Itahci Defender
800-899
1 level
9
1-25x
Madara Defender
Sasuke Defender
Kakashi Defender
900+
1 level
10
1-25x