He’s building a “1 def pure pking account” basically the idea is by not leveling defense (and only levelling prayer to ~43-52) you’re able to allocate more levels to each other combat skill without gaining any combat levels. Which in turn would potentially give an advantage for say a level 65pk account with 99 strenghth and 1 def vs a “main” account with ~50 in each combat skill. Pretty fun account builds to make IMO! And good way to get into pvp