The Irish province were champions in 2009, 2011 and 2012, and now have a chance of matching Toulouse's record of four titles (1998, 2005, 2008, 2010).
Leinster will attempt to pull off these feats to the backdrop of ongoing talks into the future of the Cup competition.
The English and French teams believe the current format is weighted in favour of the Celtic nations, notably Leinster and their Irish compatriots Munster, who won in 2006 and 2008 meaning the two teams have claimed five out of the last seven titles.
The Irish provinces' rivals in England and France claim that is partly a result of a qualification system that allows them to rest their players during the Celtic League season.
The English and French sides believe no more than six Celtic League teams should qualify, although that would put at risk the involvement of Scottish and Italian sides who currently qualify automatically.
Talks seem likely to drag on for some time to come, with the added complication of television rights deals also to be negotiated.
But the competition goes ahead as normal this season, at least, and Leinster face English underdogs Exeter on Saturday focused on one thing: extending their unbeaten European record to 16 matches.
"Right now our sole initial target is to get out of the group," said Leinster coach Joe Schmidt, who has lost just one tournament contest in 18 matches in guiding them to their last two titles.
With just eight teams from the six groups progressing to the knock-out stages, Kiwi Schmidt said his team faced a tough task, with French giants Clermont and Scarlets making up Pool 5.
"It is such a competitive pool that I think only one team will qualify for the quarterfinals so I am not thinking about anything beyond our first match against Exeter Chiefs," he said
Ulster, a third Irish province, were surprise finalists last season (but well beaten 42-14 by Leinster) and find themselves in a tough Pool Four alongside Northampton, Glasgow and Castres.
Ulster are unbeaten in five matches this season and will on Friday host Castres, who learnt this week that coaching duo Laurent Travers and Laurent Labit will leave for another club, rumoured to be Racing-Metro, for next season.
One of the main draws for fans will be Toulon, the southern French club bankrolled by Mourad Boudjellal and boasting a raft of high-calibre stars such as Jonny Wilkinson, Matt Giteau, Carl Hayman, Delon Armitage, Gethin Jenkins, Andrew Sheridan, Bakkies Botha, Chris Masoe and Frederic Michalak.
Drawn in Pool Six against Welsh region Cardiff Blues, struggling English club Sale and fellow Top 14 rivals Montpellier, Botha said he was delighted to be appearing on the European club stage.
"It's a great challenge for me but also for the team to test ourselves against the best," said the veteran Springbok lock.
"It's the highest of the high in rugby. When you see the level of the Top 14 and only six teams qualify for the European Cup, you quickly understand that this competition is particularly elevated."
Two-time champions Leicester (2001, 2002) have been drawn with French giants Toulouse, Welsh region Ospreys and the Italians of Treviso in Pool Two.
English champions Harlequins have been handed a slightly more favourable draw in Pool Three alongside two-time finalists Biarritz, the fourth Irish province Connacht and Zebre, the Italian club that has taken the place of the now-disbanded Aironi.
Saracens will also be hoping to fly the English flag in Pool One, up against Munster, Racing-Metro and Edinburgh, whose impressive performances last season will stand themselves in good stead for a go at getting to the knock-out phase.
All the teams and match details for Round One:
Friday, October 12
Ospreys v Treviso
(Liberty Stadium, Kick-off: 20.00, 19.00 GMT)
Teams:
Ospreys: 15 Richard Fussell, 14 Hanno Dirksen, 13 Andrew Bishop, 12 Ashley Beck, 11 Eli Walker, 10 Dan Biggar, 9 Kahn Fotuali'I, 8 Jonathan Thomas, 7 Justin Tipuric, 6 Ryan Jones, 5 Ian Evans, 4 Alun Wyn Jones (captain), 3 Adam Jones, 2 Richard Hibbard, 1 Ryan Bevington.
Replacements: 16 Matthew Dwyer, 17 Duncan Jones, 18 Aaron Jarvis, 19 George Stowers, 20 Sam Lewis, 21 Rhys Webb, 22 Matthew Morgan, 23 Thomas Isaacs.
Treviso: 15 Luke McLean, 14 Ludovico Nitoglia, 13 Tommaso Benvenuti, 12 Alberto Sgarbi, 11 Tommaso Iannone, 10 Kristopher Burton, 9 Tobie Botes, 8 Manoa Vosawai, 7 Alessandro Zanni, 6 Simone Favaro, 5 Valerio Bernabo, 4 Antonio Pavanello (captain), 3 Bees Roux, 2 Leonardo Ghiraldini, 1 Alberto De Marchi.
Replacements: 16 Enrico Ceccato, 17 Ignacio Fernandez-Rouyet, 18 Pedro Di Santo, 19 Francesco Minto, 20 Paul Derbyshire, 21 Robert Barbieri, 22 Fabio Semenzato, 23 Andrea Pratichett.
Referee: Neil Paterson (Scotland)
Assistant referees: David Changleng (Scotland), Bob Nevins (Scotland)
TMO: Jim Yuille (Scotland)
Ulster v Castres
(Ravenhill, 20.00, 19.00 GMT)
Teams:
Ulster: 15 Jared Payne, 14 Tommy Bowe, 13 Darren Cave, 12 Paddy Wallace, 11 Andrew Trimble, 10 Patrick Jackson, 9 Paul Marshall, 8 Stephen Ferris, 7 Chris Henry, 6 Iain Henderson, 5 Dan Tuohy, 4 Johann Muller (captain), 3 John Afoa, 2 Rory Best, 1 Tom Court.
Replacements: 16 Rob Herring, 17 Callum Black, 18 Adam Macklin, 19 Lewis Stevenson, 20 Mike McComish, 21 Ruan Pienaar, 22 Luke Marshall, 23 Craig Gilroy.
Castres: 15 Romain Teulet, 14 Marcel Garvey, 13 Seremaia Bai, 12 Daniel Kirkpatrick, 11 Marc Andreu, 10 Pierre Bernard, 9 Thierry Lacrampe, 8 Pedrie Wannenburg, 7 Yannick Caballero, 6 Piula Faasalele, 5 Rodrigo Capo Ortega, 4 Matthias Rolland (captain), 3 Michael Coetzee, 2 Mathieu Bonello, 1 Yannick Forestier.
Replacements: 16 Marc-Antoine Rallier, 17 Gregory Marmoiton, 18 Hai Lazar, 19 Joe Tekori, 20 Antonie Claassen, 21 Rory Kockott, 22 Paul Bonnefond, 23 Thomas Sanchou.
Referee: Andrew Small (England)
Assistant referees: Martin Fox (England) , Stuart Terheege (England)
TMO: Geoff Warren (England)
Saturday, October 13
Zebre v Connacht
(Stadio XXV Aprile, Kick-off: 13.35, 12.35 GMT)
Teams:
Zebre: TBC
Connacht: TBC
Referee: Leighton Hodges (Wales)
Assistant referees: Wayne Davies (Wales), Greg Morgan (Wales)
TMO: Nigel Whitehouse (Wales)
Racing Metro v Munster
Stade de France, Kick-off: 13.35, 12.35 GMT)
Teams:
Racing Metro: TBC
Munster: TBC
Referee: Greg Garner (England)
Assistant referees: David Rose (England), Andrew Pearce (England)
TMO: Trevor Fisher (England)
Edinburgh v Saracens
(Murrayfield, Kick-off: 13.35, 12.35 GMT)
Teams:
Edinburgh: TBC
Saracens: TBC
Referee: John Lacey (Ireland)
Assistant referees: Michael Black (Ireland), Olly Hodges (Ireland)
TMO: Peter Ferguson (Ireland)
Leinster v Exeter Chiefs
(RDS, Kick-off: 15.40, 14.40 GMT)
Teams:
Leinster: TBC
Exeter Chiefs: TBC
Referee: Pascal Gauzere (France)
Assistant referees: Jean-Luc Rebollal (France), Cyril Lafon (France)
TMO: Daniel Irazoqui (France)
Clermont Auvergne v Scarlets
(Stade Marcel Michelin, Kick-off: 15.40, 14.40 GMT)
Teams:
Clermont Auvergne: TBC
Scarlets: TBC
Referee: Peter Fitzgibbon (Ireland)
Assistant referees: Paul Haycock (Ireland), Simon McDowell (Ireland)
TMO: Dermot Moloney (Ireland)
Harlequins v Biarritz
(Twickenham Stoop, Kick-off: 18.00, 17.00 GMT)
Teams:
Harlequins: TBC
Biarritz: TBC
Referee: George Clancy (Ireland)
Assistant referees: Leo Colgan (Ireland), John Carvill (Ireland)
TMO: Marshall Kilgore (Ireland)
Sunday, October 14
Sale Sharks v Cardiff Blues
(Salford City Stadium, 12.45, 11.45 GMT)
Teams:
Sale Sharks: TBC
Cardiff Blues: TBC
Referee: Jérôme Garces (France)
Assistant referees: Patrick Péchambert (France), Sébastien Cloute (France)
TMO: Jean-Marie Piraveau (France)
Northampton Saints v Glasgow Warriors
(Franklin's Gardens, Kick-off: 12.45, 11.45 GMT)
Teams:
Northampton Saints: TBC
Glasgow Warriors: TBC
Referee: Romain Poite (France)
Assistant referees: Christophe Berdos (France), Stéphane Boyer (France)
TMO: Daniel Gillet (France)
Toulouse v Leicester Tigers
(Le Stadium, Kick-off: 15.00, 14.00 GMT)
Teams:
Toulouse: TBC
Leicester Tigers: TBC
Referee: Nigel Owens (Wales)
Assistant referees: Sean Brickell (Wales), Jon Mason (Wales)
TMO: Derek Bevan (Wales)
Toulon v Montpellier
(Stade Felix Mayol, Kick-off: 20.00, 19.00 GMT)
Teams:
Toulon: TBC
Montpellier: TBC
Referee: Wayne Barnes (England)
Assistant referees: Luke Pearce, Paul Dix
TMO: Graham Hughes
Source: Rugby 365
