I'm using the best work around i can think of for this now. Basically i have scripted when the dragon gets equal to or bellow a certain value of health, it is disabled, and simultaneously a ground dragon is enabled. The ground dragon has a package on it telling it to sit, as well as an ability i made from the dragonrend spell effect. This results in it spawning on the ground, and the ability prevents it from flying when initiating combat. The ground dragon does not clip through walls and so can be killed like normal. Thanks for your help guys :)