Our first preview ahead of the European Champions Cup looks at Pool 1, containing Oyonnax, Saracens, Toulouse and Ulster.
Four-time champions Toulouse will be desperate to get back on top on the European stage, but face tough games with Saracens and Ulster.
Let's take a closer look at the teams.
The great success story in the Top 14 over the last two years since their promotion, 2015/2016 is not going smoothly for Oyonnax as they take part in Europe's top competition for the first time.
Losing long-time coach Christophe Urios at the end of last season along with a number of key players such as Benjamin Urdapilleta and Antoine Tichit has proven to be a hammerblow. Oyonnax sit in the relegation zone in 13th with only two wins from their first eight games in the Top 14 this season.
That slow start is enough for new boss Olivier Azam to start being concerned about the drop – so having to battle on two fronts against three top sides in Saracens, Toulouse and Ulster isn't ideal. If Oyonnax are to progress then the Stade Charles-Mathon will have to continue to be the giant-killing fortress we've seen it turn into during Oyonnax's stint in the Top 14.
Key players for Azam's side will be hooker Jérémie Maurouard, a signing from Racing 92 who already has four tries to his name, along with fly-half Nicky Robinson. Urdapilleta's boot clinched several tight matches for Oyonnax over the last two years – now Robinson has to do the same.
The underdogs in Pool 1, and by some way, may seriously struggle on the road.
One to watch: Maurie Fa'asavalu
Hard graft isn't in short supply for Oyonnax in the back row – when you factor in Valentin Ursache, Pierrick Gunther and Viliami Ma'afu – but even at 35, Fa'asavalu proved during the Rugby World Cup that he still can pack a punch with the ball in hand. Oyonnax will need those hard yards.
Outstanding in their run to the Premiership title after sneaking into the play-offs, Saracens are still waiting to taste European glory after reaching the final in 2013. Clever signings backed up with an unbeaten start to the season through four games mean that all is looking well at Allianz Park.
No squad in England has better depth that Mark McCall's group and in Owen Farrell they have a match-winning kicker, meaning all of the ingredients are there for success. But is the year that Saracens finally make the breakthrough? And do they have enough to really put away the top sides in the knockout stages? That's the burning question.
Young guns such as Jamie George and Maro Itoje can strengthen their England chances with big performances in the competition but David Strettle's production on the wing from last year's campaign has to be replicated by Chris Wyles or one of Catalin Fercu and Mike Ellery. Will Fraser too could be a huge performer, fitness permitting.
Last year's semi-final in Saint-Etienne ended in a narrow loss to Clermont where Saracens showed no lack of heart and guts, but were undone by Wesley Fofana's moment of magic. Saracens might need a few of those themselves to overcome tough battles with Toulouse and Ulster.
One to watch: Chris Ashton
Rejected by England for the Rugby World Cup, Ashton's try record at domestic level speaks for itself. He still has a knack for coming up with key scores in the biggest games and remains as deadly a finisher as ever. Just now with an extra point to prove.
For the first time ever Toulouse will begin a European campaign without Guy Novès steering the ship, which seems insane. Ugo Mola is the new head coach ably assisted by two Toulouse veterans in Jean-Baptiste Elissade and William Servat while Fabien Pelous handles off-field matters. The new combination has a hell of a job on its hands though to match the four European titles won by Novés.
It's been five long years though since Toulouse last triumphed on the big stage, back in 2010 against Biarritz, as the most ever successful side in Europe have watched first Leinster and then Toulon take control of the competition with multiple titles. Twice in the last three years they have failed to qualify out of the group.
A bright start to the Top 14 this season however is cause for optimism. Six wins out of eight games leave Toulouse just two points off the top of the table, capped off by last weekend's 52-12 thrashing of Grenoble at home. Gaël Fickou and Toby Flood have started the season sharply too with four tries apiece.
There's no questioning that Toulouse have enough grunt in their pack – spearheaded by Louis Picamoles, Yoann Maestri and Census Johnston – combined with lethal finishers in the backs like Fickou, Yoann Huget, Maxime Médard and new man Paul Perez.
But whether the coaching changes will be able to reverse Toulouse's fortunes in Europe so soon after taking over is the main wonder.
One to watch: Thierry Dusautoir
The France captain penned a new two-year contract extension at the start of the year to remain with Toulouse until he's 35. But more monstrous tackling numbers in the Rugby World Cup for les Bleus reminded us just how good Dusautoir still is, and he can swing games on his own.
Rounding out Pool 1 are the Irish giants whose 1999 European Cup title feels very far in the distant past, despite reaching the final in 2012 when they were beaten by Leinster at Twickenham.
Ravenhill has served up many a memorable European night and welcoming both Saracens and Toulouse to Belfast will be no different, as a fantastic home support do their best to send away the opposition with their tails between their legs.
Ulster though feel like a group in transition as young talents like Iain Henderson and Stuart McCloskey are ushered into the spotlight to join an established cast including Ruan Pienaar, Chris Henry, Rory Best, Andrew Trimble and Darren Cave. New director of rugby Les Kiss only took up his role with the province following Ireland's World Cup exit and naturally is yet to really put his stamp on the side.
Last season was a huge disappointment as Ulster exited the competition at the group stages, a year on from having battling to away wins at Montpellier and Leicester. Achieving wins on the road of that magnitude at Allianz Park or the Stade Ernest-Wallon though is some ask – and Ulster have started the PRO12 season with four wins out of seven.
One to watch: Ruan Pienaar
Charged with getting the best out of young talents like McCloskey and Stuart Olding, Pienaar is also such a difference-maker with the way he can control matches off the kicking tee. This is his sixth season with the Irish province, where he has become an embedded asset, with his contract expiring in 2017.