Every time you kill a Giant Plant in garden you got the chance of Mystical ENT respawn near you, the same method do Ettine Master or Ettine Avenger respawn near you while you killing Ettines, in this same method respawn eternal dragons and ndragons when you kill fire-wyvern, they respawn to protect the other monsters

Is also called respawn event the respawn of multiple mob spawns near the player activity, the chance increase where are to much players togheter.