The Transylvanian Beagle Boys are a group of anthropomorphic dogs.
Most probably the direct descendants of the thieves who opposed the first Count Duckesque, the Transylvanian chapter of the Beagle Boys continued their forebears' attempts to lay hands on the Duckesque treasure, but kept failing at conquering the castle, in large parts due to being so underfunded that they still used the same medieval equipment as their ancestors — ladders and crossbows and so on.
In 1986, when American Beagle Boys came to Castle Duckesque tracking Donald Duck, their Transylvanian counterparts helpfully loaned them their equipment; the American Beagles were appalled at how out of date it was, and arranged to purchase dynamite through other means, finally succeeding at destroying the Castle as a result — though they did not, of course, get to keep the treasure.
Behind the scenes
The Transylvanian Beagle Boys first appeared in 1986 in Donald Duck and the Adventure in Transylvania.