Heineken Cup holders Toulon have been grouped with Cardiff Blues, Glasgow and Exeter Chiefs at the draw for the 2013/14 competition.
It is the second year running that the French side will take on the Blues while stern tests await against the impressive Warriors and Chiefs.
2012/13 finalists Clermont are drawn in arguably the toughest of the six pools, facing Harlequins, Scarlets and the big-spending Racing-Metro.
The other groups will see PRO12 champions Leinster take on Top 14 winners Castres, with Saints and the Ospreys completing Pool 1.
Toulouse and Saracens will be licking their lips after being drawn with Connacht and Zebre, the latter duo going up against each other again.
Pool 5 pits Ulster, Leicester, Montpellier and Treviso together while Munster, Perpignan, Edinburgh and Gloucester go toe-to-toe.
The Amlin Challenge Cup draw sees 2012/13's finalists Stade Francais take on London Irish, Cavalieri Prato and Olympus while the toughest Pool seems to be the one possessing Biarritz, Sale, Worcester and Oyonnax.
Pool 1 - Leinster, Northampton, Ospreys, Castres
Pool 2 - Toulon, Cardiff Blues, Glasgow, Exeter
Pool 3 - Toulouse, Saracens, Connacht, Zebre
Pool 4 - Clermont, Harlequins, Scarlets, Racing
Pool 5 - Ulster, Leicester, Montpellier, Treviso
Pool 6 - Munster, Perpignan, Edinburgh, Gloucester
Amlin Challenge Cup
Pool 1 - Biarritz, Sale, Worcester, Oyonnax
Pool 2 - Bath, Dragons, Bordeaux-Begles, Mogliano
Pool 3 - Brive, Newcastle, Calvisano, Bucuresti
Pool 4 - London Wasps, Viadana, Bayonne, Grenboble
Pool 5 - Stade Francais, London Irish, Cavalieri Prato, Olympus