Clermont Auvergne and Stade Français are among the potential opponents for Saints in next season's Challenge Cup.
A list of 19 participants - one more club is still to be confirmed - was released on Thursday, with five Premiership teams involved.
Sale Sharks, Harlequins, Worcester Warriors and Bristol Bears will be alongside Saints in the draw, which will be made on Wednesday, June 20 in Lausanne.
And there are some powerful Top 14 teams joining them, with La Rochelle, Pau, Clermont, Bordeaux-Bègles, Agen, Stade Français, Perpignan and Grenoble all taking part.
Russia’s Enisei-STM have booked a place once again after retaining their Continental Shield title.
However, Heidelberger RK, who were losing Continental Shield finalists in Bilbao last season, are ineligible to compete in next season’s Challenge Cup following a decision by EPCR.
A replacement club will be announced shortly.
The 2017/18 Challenge Cup final was held at Bilbao’s San Mamés Stadium, with Cardiff Blues edging out Gloucester Rugby 31-30 in front of 32,543 spectators.
Next season's showpiece will take place in Newcastle.
CHALLENGE CUP 2018/19
Gallagher Premiership Rugby (5): Sale Sharks, Saints, Harlequins, Worcester Warriors, Bristol Bears
Guinness PRO14 (5): Benetton Rugby, Ospreys, Connacht Rugby, Zebre Rugby Club, Dragons
TOP 14 (8): La Rochelle, Pau, ASM Clermont Auvergne, Bordeaux-Bègles, Agen, Stade Français Paris, Perpignan, Grenoble
Continental Shield (2): Enisei-STM, TBC