Ronan O'Gara will take the next step in his coaching career with Top 14 side La Rochelle after the Irishman opted to leave the Crusaders.
The teams who finished first and second in the Top 14 regular season will contest the final after Clermont Auvergne got the better of Lyon.
Toulouse booked their place in a Top 14 final for the first time since 2012 after they overcame La Rochelle in Bordeaux.
Lyon booked a Top 14 semi-final against Clermont after a hard-fought 21-16 victory over Montpellier on Saturday.
La Rochelle finished behind Racing 92 in the Top 14 regular season but dumped the Paris club out of the play-offs on Friday.
There will be a new Top 14 champion after Castres missed out on a top-six finish with a final-day defeat to Toulon.
Neither Bordeaux Begles nor Stade Francais can make the play-offs in the Top 14 after suffering painful defeats in the penultimate round.
Perpignan suffered a 23rd loss in 25 Top 14 games as Louis Dupichot and Simon Zebo scored hat-tricks in Racing 92's 52-14 victory.
Handre Pollard has agreed to join Top 14 heavyweights Montpellier and Morne Steyn will return to his homeland to replace the fly-half.
Morgan Parra was injured in Clermont Auvergne's European Challenge Cup final triumph and will play no further part in his club's season.