Defending Super League champions Wigan Warriors will face St Helens for a place in the grand final after beating Salford Red Devils 18-12.
Tries from Adam Milner and Jordan Rankin helped Castleford Tigers to victory on the road in a hard-fought elimination final.
Former New Zealand international Shaun Kenny-Dowall is heading for Super League after signing for Hull Kingston Rovers.
London Broncos' brave bid to retain their Super League status came up short, while Salford Red Devils claimed third place in the table.
Wigan Warriors scored four second-half tries to guarantee home advantage against either Warrington or Salford in week one of the play-offs.
After serving as interim boss at Newcastle Knights, Kristian Woolf will swap the NRL for life in Super League with St Helens.
Richard Agar stepped into an interim coaching role with Leeds Rhinos in May and has now earned a 12-month rolling deal.
Jay Pitts' late try means London Broncos remain in with a chance of beating the drop, while also leaving Hull KR in deep trouble.
Castleford Tigers boosted their Super League play-off hopes by overcoming Hull FC courtesy of a Jake Trueman masterclass.
Five players from outside of England's latest development squad have been selected in Wayne Bennett's Great Britain Lions performance squad.