how to kill dwarf leader

i need help on how to eliminate the dwarfs. i went down to the pit and found out the correct footpath but cant kill the leader by any means. also still there's a dwarf outside that i cant kill without misstepping.

I know this is late but in case anyone comes here looking in the future - you have to smash the pillars to the west.

Honestly, I haven't played this expansion, but as far as I know from other players, the Dwarf Leader is invincible. You won't be able to damage him in any way.

You can kill him after smashing the pillar to the west.