Seeking a fantasy series from the 80s/90s. In the series was an inept wizard who carried a satchel full of rune sticks leftover by a long lost race called the Rebus/Rhebus/Rhybus (I'm not 100% sure of the spelling). The wizard often failed because he had trouble decoding the rune sticks. Eventually his satchel caught fire and he lost them all. The enemies in the books were somehow made of ice and wary of sunlight - I think they were dark elves. When killed, they would degrade into a puddle of dirty water. In one of the books was a character who flew around inside a cavern while wearing an old-fashioned helmet with a hinged visor. He could blast fire from his eyes and regularly chuckled while firing at the trolls below. Any help finding this series would be much appreciated.