Trusty as a troll.
More Icelandic Proverbs:
A man's will can be his paradise, but it can also be his hell.Icelandic
Every man likes the smell of his own farts.
Icelandic
The sun that melts the wox is the same that hardens the mud.
Icelandic
There are seven different kind of weather in one autumn night.
Icelandic
It is difficult to steal when the boss is a thief.
Icelandic
Sin is not perfect until one prides oneself on it.
Icelandic