It's been a long, hard journey. Our heroes have fought through hordes of monsters and mooks. They've finally reached the enemy fortress, and it's time to take out the Big Bad before he can release the Sealed Evil in a Can! But wait, what's this? As they strike him down, with his dying breath he manages to finish the incantation! Watch out heroes, the Sealed Evil lives again!
This trope thrives in stories where the entire plot has revolved around reviving some ancient evil, and the summoner is at the very end of the journey. This summoner dies, but shouts the trope name (or something similar to it), and the Ancient Evil springs to life so the heroes can crush it forever. It's often used as a ticket to a great climactic Final Boss, when a development team is unable to reach a more fluid transition. Also avoids a very anticlimactic conclusion; how wimpy the ending would be if the heroes reached the end after hearing so much about the Sealed Evil, fought the summoner, and never fought the real villain!
Probably a sub-trope of Dying Curse.
Warning: Spoilers abound!
- In the first Hellboy movie, Rasputin summons the Ogdru Jahad this way — if it wasn't a case of Ogdru Jahad simply being released by Rasputin's death, in which case Nice Job Breaking It, Hero!.
- Khan did this Star Trek II: The Wrath of Khan before activating the Genesis device. It's not technically a summoning, but it follows pretty much the same form.
- A dwarf, betrayed, abandoned, and left to die does this in Thud! and writes a mine sign that will summon the Summoning Dark, a "quasidemonic thing of pure vengeance." Fortunately for Sam Vimes, he harbors an even more powerful entity than the Summoning Dark whose job is to keep all of Sam's darker tendencies locked away.
- In the Warhammer 40,000 universe, and particularly in the RPG Dark Heresy, this is an omnipresent danger when trying to stop cults from summoning a demon. Especially when that cult is dedicated to Khorne, where spilling the cultists' blood is equally pleasing and empowering to Khorne as them spilling yours. "Khorne does not care from whence the blood flows, only that it flows."
- Terraria: The Lunatic Cultist summons the four Celestial Towers when defeated.
- Shining Force 1 revolves around the story of Darksol, an evil sorcerer, trying to revive Dark Dragon to take over the world. The heroes fight him in Dark Dragon's lair, and as he's about to die, Darksol shouts the trope namer and Dark Dragon is brought to life as the Final Boss.
- The King of Fighters '97. The plot revolves around three young adults trying to revive Orochi of Japanese folklore since their leader was defeated in the last game (KOF '96). After you defeat the 3 characters, it is discovered that one of the characters is in fact the vessel that Orochi is being summoned through and with their final strength, the remaining two give their energy and their lives to the character so that he transforms. Thus the final boss battle begins.
- In Silent Hill 3, in the final confrontation against Claudia Wolf, Claudia takes the fetus that Heather rejected... and eats it herself, killing her in the process but summoning the demon god for the final battle.
- In Jedi Knight: Jedi Academy, if following the Light Side, Jaden has to fight against Tavion, the leader of the Disciples of Ragnos who are trying to resurrect the old Sith Lord. When she loses to Jaden, she leaps on top of the statue of Ragnos, thrusts in his reviving scepter, and then gives up her body so he can possess it and get revenge.
- In The Legend of Zelda: Oracle Games, at the end of a linked game, You fight Koume and Kotake before they can sacrifice Zelda to revive Ganon. So, they sacrifice themselves instead, and Ganon comes back without his mind.
- Something similar happens in The Legend of Zelda: Skyward Sword, the final confrontation with Ghirahim takes place as he's working a ritual to free Demise from his imprisonment. Ghirahim continues his ritual during the battle and finishes it just before Link can deal the finishing blow.
- Barlowe does this to revive Dracula in Castlevania: Order of Ecclesia.
- At the conclusion of Final Fantasy IV, a dying Zemus vows to keep fighting. That vow causes his hatred to become the final boss, Zeromus.
- Fire Emblem: The Blazing Blade has Nergal summon a dragon as he dies. (This is actually something of a tradition for the series, but this is the best-known example.)
- Golden Sun: At the end of the first game, the party fights Saturos and Menardi. On defeat, they fuse into a giant dragon, but this still isn't enough.
- Dehuai of Shadow Hearts lets off one of these to summon the fury of the earth incarnate. The miserable old jerk was trying to complete his ritual for years, but when you finally finish him off, he realizes he has nothing left to lose and sacrifices his own life-force to complete it. Made an Anti-Climax when it turns out the ritual was too costly for even that to set it off... until Bacon shows up and decides to give it one last push. With what comes forth, you can see why the figurative engine stalled.
- Skyblazer: Sky successfully defeats Ashura and rescues the sorceress, but Ashura sacrifices the last of his strength to summon his master, Raglan Lord of Darkness.
- While it doesn't deal with Sealed Evil in a Can, the League of Legends teaser for Kalista, titled The Pledge, depicts her being summoned in this manner.