Of the 10 matches played on Tuesday, only one saw a club overturn a first leg deficit. That came from Shamrock Rovers, who beat Floriana 5-1 at Tallaght Stadium to complete a 5-3 aggregate win.
After losing the opening leg 2-0, The Hoops went to work right away, scoring seven minutes in at home. While the Maltese champions responded less than 10 minutes later, Shamrock showed their composure, netting a second before the half-hour mark before a three-goal haul after the break saw them past Floriana.
Five different players scored for the Dublin-based side, who are now through to the second qualifying round. It is the third time in their last four appearances in UCL qualifying in which they have prevailed at this stage.
Next for Shamrock are Ararat-Armenia, who saw off an attempted comeback from Riga FC to advance 4-3 over the two legs.
The Armenians lost 3-2 on the road, having seen their 2-0 first leg lead evaporate in the opening quarter of the match. However, they did not panic, and thanks to goals from Zhirayr Shaghoyan and Sandro Lima, they were able to fight their way past their Latvian opposition.
In what was perhaps the most dramatic game of the day, KuPS Kuopio overcame Vardar in extra time despite a 3-2 home loss. A Goran Zakaric penalty in the 91st minute forced extra time as the visitors erased a 2-0 loss from their home leg.
The first period of extra time saw the sides trade goals in the space of two minutes before a Piotr Parzyszek penalty moments later ultimately decided the tie, where the Finnish side prevailed 4-3 overall.
Iberia 1999 advanced from a UCL tie for the second time - seven years on from the previous occasion - after they held off Flora Tallinn 5-4 on aggregate. A 2-2 result in the Georgian capital proved to be enough for the Red Eagles.
Also advancing after a 2-2 draw were Vikingur Reykjavik, who got the better of Gyor in Hungary. After the hosts levelled the aggregate score going into the break, former Everton midfielder Gylfi Sigurdsson grabbed what proved to be the deciding goal 10 minutes into the second half.
Next for the Icelandic side are Israel's Hapoel Be'er Sheva.
Kauno Zalgiris steal late winner as Levski dominate
Lithuania's Kauno Zalgiris provided the late drama in their match against Drita. With the score tied 3-3 going into stoppage time in Prishtina, Amine Benchaib scored a penalty in the 94th minute to send his side through.
The visitors triumphed 3-2 on the road to complete a 4-3 victory across the two legs, making it the second straight summer where they will be involved in the third qualifying round of a UEFA club competition.
Drita, who reached the UECL knockout stages last term, will have to try and get through three rounds of qualifying in the competition over the next six weeks.
Elsewhere, Levski Sofia enjoyed a 4-0 success over Borac Banja Luka at home. Reinaldo scored a six-minute brace for the Bulgarians, who did their damage in the second half to progress 5-1 on aggregate. They were also the only side to complete a clean sheet in Tuesday's play.
Larne finished off nine-man Tre Fiori 2-1 to advance 3-1 in total. It was their first time successfully negotiating a UCL tie.
Lincoln Red Imps are also through to the second qualifying round for the third year running after beating Andorran side Inter Club d'Escaldes 4-2 over the two legs. The latter did manage to avoid defeat at home, earning a 1-1 draw. As for Sabah Baku, their maiden UCL run will go on after finishing off The New Saints 2-1 away, and 4-1 overall.
Wednesday will have the remaining four ties in the first qualifying round. CS Universitatea Craiova will look to get the job done at home to ML Vitebsk, while Atert Bissen have work to do against KI Klaksvik. The same can be said for Sutjeska, who have a one-goal deficit to overturn against Kairat Almaty, with Egnatia and Petrocub all square from the first leg.
The losing sides transfer to the Conference League domestic champions path, starting in the second stage of qualification. Exceptionally, Tre Fiori and Inter Club d'Escaldes will enter a round later at the third qualifying round due to rebalancing.