To date they have won four of their 16 clashes at all stages with Irish provinces and beat Leinster 18-15 in 2008/09. Their one previous trip to the RDS ended in a 33-3 defeat.
An 80 metre interception try by wing Romain Martial set Castres on their way to a first round victory over Northampton Saints. The rest of the points in the 19-13 win came from the boot of South African scrum half Rory Kockott.
Leinster not only picked up an away victory in round one, but also landed a late, late penalty by Heineken Cup debutant Jimmy Gopperth to deny the Ospreys a losing bonus point. That could be vital in the final analysis in this tough Pool.
Sean O'Brien picked up the Heineken Man of the Match award, as well as the game's only try, and Leinster were far too streetwise for their big PRO12 rivals. Skipper Jamie Heaslip marshalled the defensive line superbly well and the Ospreys could only muster three Dan Biggar penalties in a costly 19-9 defeat.
Saints skipper Dylan Hartley saw his try rescue a losing bonus point for his side in the second half at Stade Pierre Antoine. Now he will have to find a way to win at Franklin's Gardens in round two when the Ospreys come calling on Sunday.
The front row battle between British & Irish Lions team mates Alex Corbisiero and Adam Jones will be worth the admission price alone, while aspiring Wales wing Eli Walker will have to try to find some way to stop George North.