Saracens came back from a 17-11 half-time deficit to beat Harlequins 31-17 at Allianz Park on Saturday and book their place in the English Premiership final.
Two late tries earned Northampton a place in the English Premiership final with a 21-20 victory over Leicester.
Harlequins edged Bath 19-16 to grab a place in the Premiership play-offs after a remarkable late-season run.
Saracens put out their strongest team to beat lowly Worcester 44-20 on Saturday and secure a home semi-final in the English Premiership.
A weakened Saracens all but confirmed their place at the top of the English Premiership with a tough 23-18 win over Newcastle.
The top six English clubs are still fighting for Premiership play-off positions, but at least they have secured their place in the new European championship next year.
Saracens survived a late fightback from Northampton to stretch their lead at the top of Premiership to 10 points.
Bath maintained their challenge for an English Premiership play-off place with a dramatic late victory over 11-man Gloucester.
Saracens cemented their place at the top of the English Premiership as their rivals became involved in a dog-fight for play-off places.
Saracens soared to the top of the English Premiership with an emphatic 39-17 win over Harlequins in front of a world record club crowd of 83,889 at Wembley.