No bad questions! They are slayer instruments which increase you barding success chance for the respective monster types listed.
They drop the barding difficulty for the mobs affected by the slayer type. To check slayer´s different types see this thread: http://uorforum.com/threads/renaissance-guide-to-slayers.1601/ On a sidenote, join UOR discord channel! Great place to clear doubts, chat, trade, etc https://discord.com/channels/565638357720367114/565638357720367118 EDIT: You should also check this thread: http://uorforum.com/threads/zagygs-skills-guides-provocation.1242/ Good explanation of how provocation works in numbers and how slayer instruments affect it.
For provo you need to either have two of the affected targets (blood drinking=blood ele Slayer, etc) or target the blood ele first if you are provoing different targets. Otherwise it acts in reverse and will make it more difficult.
Great tip @Holden - did not know about increasing difficulty, and I use provo on most of my main characters!
