So here is the way to pay only 3 Gold for entry.
1. Talk with grog, get quest to kill marg
2. talk with marg, tell him about the quest. Leave with the remark to kill the real one
3. go to grog. TALK with him first and tell him about margs regards. Kill him.
4. go to marg tell him about grog's death and pay the reduced fee of 3 gold with the condition to tell about voidwalken stories.
How to kill grog at lvl 9-10 (what I did)
He is not immune to charmed and stunned. Grog does not have magical armor. Begin with charmed arrow or respective skill in summoning.
reduce his physical armor, burn everything (fire arrow/necrofire with cursed potion flasks if you have those)
from there on either have many chars with shocking skills or weapons with high chance to stun. continue to stun and burn him.
about 10-15minutes later he should be dead.
(a great way to keep burning him is to have a summoner with totems/incarnate and make them fire elemental.
this way he is stunned throughout the match and you can keep damaging him until he is done.
Enjoy being awesome! :)