Its often just said that Gohlbrorn is the Dwarvish word for Bulette in Forgotten Realms. But if you go back to AD&D 2nd Edition, Dragon Magazine did a special stat block for the Gohlbrorn, separate from the Bulette. It was intended to be the smaller, quicker and meaner Underdark version. I’ve attempted to update the 2E stat block to 5E by comparing the relative abilities between the Bulette and the Gohlbrorn in 2E and then using the Bulette from the 5E Monster Manual. I also had to take some liberties by using the WOTC Guide to Conversion for 5E. Let me know what you think.