how to add Event monsters

As i remember on gmo , there were events in lost towers .... this special event monsters looks like jumping umbrellas.

https://www.youtube.com/watch?v=WbKctlQ6M7c

My question: how can i add this special mobs ..
i posted this question 1 year ago.. but sadly there was no answer for this.
Anyone can help me ? thank you

its looks like blue event ^^ u can also change mob.. and where did they spawn..