The Scald was the Real thief 

EXPLANATION:

He lied more than 4 times 

1.There were 6 Jarls on the table But Scald mentioned only 5 ( Scald is not a Jarl)

Another notable thing is that he Has to write all the Jarl's story But he missed the story of ULF and He Added Einar

2. Bjorn was the biggest and Strongest of all the jarl But Later Einar was described as the strongest

3. Ivar remained seated while telling his story But Later He Mentioned That Ivar Sat down and gave floor to Ragnar

4. Loki was the elder brother of Ragnar But Later He Mentioned That Loki tried to interrupt his elder Brother: Ragnar

5.Loki Stood up and Rearranged his breastplate and again Scald mentioned that Loki stood up and Bowed before all jarls 

All of these Are enough to prove that Scald lied more than 4 times 

And another Reason is that None of the other lied more than 4 times

That's all , I am participating in Every Quiz Competition and Always spending Many Time to solve it on my own , but U guys always give the Prize to the ones who Copy others or you guys simply use Random Comments generator

I will be Waiting for the Prize and I didn't copy anyone

Scald

Scaled

Scald lied. The beginning says that the thief lied more than 4 times. Here they are:

1. Scald said that there were 6 Jarls at the feast, then lists 5

2. Scald said that Ivar was unable to stand, due to an injury, then says he sat after telling his tale

3. Scald said that Bjorn raised a horn, but then it was a goblet

4. Ragnar had an older brother Loki, but then says Loki tried to interrupt his older brother Ragnar

5. Scald said he slapped his palms (plural) on the table, but then says he lifted his hand from Loki after telling his tale.

6. Scald says Loki stood to tell his tale, then stood after telling his tale