Jamanra the copper citade boss

Hi, I just had very bad experience in the situation with Jamanra the copper citadel boss. Right after I killed the boss I died from something that I not even know without any animation and the map after that just counts as completed and Im not able to get back to collect the loot... it is really very annoying as I was preparing for that fight couple days by walking around and taking towers to get max loot Im not even counting here how much time I wasted to find that citadel... also in the previous fight with this boss I died but in the middle of the fight in the situation when he was frozen and I was hitting him and just in less than second when he get out from freeze I died without any animation also not even knowing from what.