This happens to me 9 out of 10 times in Faction wars-high Elf Crypt-stage 6. You can see in the screen shot this battle here was over ten minuets and still going when i finally just exited taking the loss. All because the enemy just keeps spamming that unkillable skill. In the past i had to sit and wait till he was permitted to kill one of my guys then id be allowed to finish him. Now that my grp is stronger and he cant get that kill the battle just keep going since he just keeps spamming that lame skill that should just be tossed anyway.