https://www.youtube.com/watch?v=pSqzaMoedXY&feature=youtu.be

1. Choose The Second Encounter 'Serious' Difficulty

2. Go down and get secret rocket launcher.

3. Fire the rocket launcher right below to your feet.

4. Rocket damage will make you 50hp. Do not get the fall damage, as you see the video. while in the air, trying to fall down lake.

5. Try to lure gnaar, and this creature will attack you.

6. Kill gnaar as fast as you can while 1 hp.

7. And go to the lake, kleer skeletons will come to you.

8. Wait for the 1 minute, and achievement will be unlocked.

Good