How Much Health Would One Need to Survive the Fall of Kagrenzel

The plumet we take after we are tricked by the trapdoor of Kagrenzel is the longest fall in the entire game, but the method to surivive it is to simply fall in the water at the bottom or use Become Ethereal to, well... become ethereal.



But lets say the water at the bottom of Kagrenzel was solid rock, how much health would one need to survive such a fall? Has anyone ever spammed legendary skills and amassed enough health for such a feat before without the use of mods?