University of Ulster's bid to win a first Sigerson Cup in 10 years ended in a 0-18 to 1-13 double extra-time defeat by UCD in Inniskeen.
Brian O'Seanachain and Con O'Callaghan scored in the second period of double extra-time to win it for UCD.
After around 100 exhausting minutes there was little to separate two shattered teams.
Tyrone's Mark Bradley scored the only goal while UCD will face NUIG in Saturday's decider in Santry.
Monaghan's Conor McCarthy lit up the final quarter of normal time with four points in the last 15 minutes to put UCD 0-12 to 0-10 ahead going into added time.
However, Tyrone referee Sean Hurson played a generous six minutes stoppage time and Lee Brennan's free, followed by Derry's Gareth McKinless' 66th-minute point, forced extra-time when it finished level 0-12 each.
Bradley netted for UU two minutes into extra-time, with a close-range finish from Brennan's superb pass.
UCD took over with Evan O'Carroll deadly from placed balls and McCarthy continuing his lethal scoring form and they nudged in front in the second half of extra-time.
For the second time, the Jordanstown outfit snatched a late point to force an extension in the game - Rory Brennan's 81st-minute point tying the scores at 1-13 to 0-16 to tee up a further 10 minutes.
UU failed to score in either half of double extra time and O'Seanachain's 86th-minute point, followed by O'Callaghan's simple tap-over free, finally proved decisive as the 2016 champions booked a place in the decider for a third year in a row.
Ulster University: S Fox; M Magee, M McKernan, M McEvoy; R Brennan, R McNamee, G McKinless; T O'Brien, J Munroe; R McAnespie, M Bradley, E McHugh; L Brennan, N Madine, F Burns.
Subs: D Mulgrew for Madine (55), D Gallagher for Burns (55), D Tallon for McAnespie (60), F Burns for McNamee (70), R McAnespie for McHugh (78).
Scorers for UU: L Brennan 0-3 (1 '45', 1f), M Bradley 1-0, F Burns, R McNamee, R Brennan 0-2 each, T O'Brien 0-1 (f), N Madine, M McKernan, G McKinless 0-1 each.
UCD: C Manton; L Fortune, C O'Shea, P Healy; S Coen, C Mullaly, J Feehan; B O'Sullivan, J Barry; L Casey, C McCarthy, B Byrne; C O'Callaghan, E O'Carroll, E Lowry.
Subs: B O Seanachain for Casey (40), T Hayes for Lowry (42), L Silke for Byrne (50), P O'Connor for Feehan (70), L Moran for O'Connor (77).
Scorers for UCD: C McCarthy 0-6 (3f), E O'Carroll 0-5 (3f, 2 '45'), L Casey 0-2, C O'Callaghan 0-2 (2f), E Lowry, 0-1 (f), L Silke, B O Seanachain 0-1 each.
Referee: Sean Hurson (Tyrone)