First, Oberon started with the bows. He had a bowsmith made the crude replica of what he saw, but there was a problem. How was that bow from his dreams able to shoot arrows which had the same power as powerful mage fireballs.
Or making one arrow turned to multiple arrows without casting any spells, and with the same Canon power.
He didn't even recalled the symbols on the bow's bronze rest, above the handle, or how the rest even worked. All he remembered was that when the string was pulled, the arrow was fired with a twanging sound, through the handle.
However, after so many years, Oberon was very excited when he saw the power of his own improved bows, and almost burst into tears. He had finally succeeded. Well, he could count it as a success.
He could now protect himself from the dreads without his true powerbase and ability to cast spell. Well, he could protect himself from the low-level dreads at the least.