Dende's History
Namek Saga
Dende first appears during the Namek Saga in Moori's village on Namek, which Frieza and his henchmen, Zarbon, and Dodoria, are terrorizing in their search for the Namekian Dragon Balls. After putting up a brave stand against Frieza's henchmen, Moori is brutally killed by Dodoria, who then kills the fleeing Cargo, while Dende looks in horror, and Frieza's soldiers retrieve the village's Dragon Ball. Angered by Dodoria closing in on Dende, Gohan kicks Dodoria into a Namekian house, and with the help of Krillin, Gohan saves Dende, and they fly away from the village. Even though they manage to escape from most of Frieza's henchmen, Dodoria is sent to chase after the three and is almost successful in killing Krillin, Dende and Gohan until Krillin blinds Dodoria with a Solar Flare, and hide behind an island. After escaping from Dodoria's Maximum Buster, they sense Vegeta killing Namekians in Tsuno's village. Dende, grateful for his rescue and confident in their good intentions, guides his saviors to the Grand Elder Guru. After the grand elder reveals Krillin's true potential, Krillin leaves Dende with Guru and brings Gohan for Guru to reveal his true potential. Grand Elder Guru later reveals Dende's potential, allowing him to use his healing ability, and sends him to help Gohan and Krillin to summon the dragon Porunga because they cannot speak the Namekian language to make their wish.
Frieza Saga
Dende eventually takes part in the battle against Frieza. He mostly watches, but at times assists by healing the fighters, and saves all of their lives with his healing ability; such as Krillin after he gets impaled by Frieza, Gohan after Frieza brutally beats him, Piccolo after Frieza almost destroys him with his Crazy Finger Beams and Vegeta who wants to get a Zenkai boost to become a Super Saiyan. Reluctantly, due to the fact Vegeta had slaughtered a lot of Dende's own race, Dende heals Vegeta under Piccolo's orders. However, he pays a serious price when Frieza transforms into his final form and kills him with a single shot, in order to prevent him from healing anyone else. Later on, during Goku's battle against Frieza, Dende is revived by a wish made from Shenron and makes the wish to Porunga to transport everyone except Goku and Frieza to Earth. When on Earth, Dende realizes that Nail has fused with Piccolo. Dende lives on Earth for a while until it is time for the Namekians to be transported to New Namek.
Cell Games Saga
Later after Piccolo's fusion with Kami, Dende is teleported from New Namek to Earth at Goku's request to take Kami's vacant position. It is at this point that Dende is truly acquainted with Goku, having only caught a brief glimpse of him on Namek. After reuniting with his friends Gohan and Krillin, having not seen them in years, Dende is able to recreate the Earth's Dragon Balls, that had been powerless after Kami was fused with Piccolo, and grants Shenron the ability to grant three wishes (or two if one wish is used to wish back to life a large number of people).
Later, following the conclusion of the Cell Games, Dende heals Gohan's battle-worn body.
Majin Buu Saga
Seven years later, Dende watches the events of Majin Buu's awakening and his killing spree of almost everyone on Earth. Eventually, when Super Buu makes his way to The Lookout, he barely says anything, yet when he asks Piccolo what he is doing when he mentions that Super Buu can kill all the other Earthlings but it would take up until tomorrow, Dende is told to be quiet, or the plan will be ruined. The plan is ruined anyway when Super Buu uses the Human Extinction Attack to leave less than twenty beings on Earth within minutes. Later, he escapes the Hyperbolic Time Chamber and returns to The Lookout to begin his killing spree. However, before Dende can be turned into chocolate and eaten, Mr. Popo knocks him off the lookout to assure that the Dragon Balls will still be around to stop Buu.
Dende is faintly sensed by Gohan when he returns to Earth and after Super Buu blows himself up. Gohan, Piccolo, Goten, and Trunks then fly off to look for him, finding and saving Mr. Satan and Bee in the process. When both Piccolo and Trunks accidentally drop Mr. Satan out of the sky, they find Dende. After explaining the different situations, Buu returns, mysteriously wanting to fight Super Saiyan 3 Gotenks. After Gotenks and Piccolo are absorbed, Ultimate Gohan fights Super Buu, while Dende, Mr. Satan, and Bee watch.
From then on, Dende is seen flying, following, and hiding around with Mr. Satan and Bee, willingly explaining situations and, from time to time, getting annoyed by Mr. Satan's pigheadedness. He is saved by Tien Shinhan from Super Buu (Gotenks Absorbed) who fires a Finger Beam in an attempt to kill him and is then saved again later, along with Mr. Satan and Bee, by Goku from Kid Buu blowing up the planet. Dende is the one who suggests that they use the Dragon Balls on New Namek.
God of Destruction Beerus Saga
Dende goes to Bulma's birthday party on her cruise liner. While the Z-Fighters were battling Beerus, Dende begins to sense ki from Beerus he hasn't sensed before. After a while, Dende tells Piccolo that Beerus has divine ki, noting that he is a god. After Goku had become a Super Saiyan God, Piccolo asks Dende if he is actually a god in which Dende confirms it. Dende watches the battle between Goku and Beerus in Bulma's spaceship. Dende is in awe by the power of Beerus and Super Saiyan God Goku. In the end, Beerus is planning to destroy the Earth but he falls asleep in the process. After this, Whis takes him home.
Golden Frieza Saga
After Frieza's resurrection and four months after his training, Frieza arrives on Earth in Age 779 with a thousand soldiers to get revenge on Goku. Dende is on The Lookout when Goku teleports there to drop off Piccolo who has been killed by Frieza. Dende, along with Mr. Popo, is saddened by the sight of Piccolo's demise. He is killed when the planet explodes, but Whis uses his Temporal Do-Over technique to undo the damage, undoing Dende's death in the process.
Universe 6 Saga
Sometime after the battle with Golden Frieza, Dende is fixing the Room of Spirit and Time for Goku and Vegeta to train and for longer in preparation for the tournament on the Nameless Planet. He is playing tennis with Mr. Popo while Goku and Vegeta are training in the Hyperbolic Time Chamber.
Copy-Vegeta Saga
Dende attends the victory celebration party at Capsule Corporation with everyone else following the Universe 6 vs Universe 7 tournament.
"Future" Trunks Saga
At The Lookout, Dende is with Mr. Popo as they witness Vegeta destroying the Hyperbolic Time Chamber during his training after losing to Goku Black and Future Zamasu the second time, causing a huge crater in The Lookout. Despite this, Dende still wishes Vegeta good luck in resuming the battle against Goku Black.
Universe Survival Saga
Goku approached Dende so that he might help him to find Android 17, to take part in the Tournament of Power. Dende used The Lookout as a means of transport to get to the Southern Island, where Android 17 resided.
Later at The Lookout, Dende tells Goku that Uub (at this point still unnamed) lives in a village, and although he is young, he is a brilliant martial artist. Dende suggests that when Goku and Uub cross paths, he should train him. Goku says he isn't good at that sort of thing. Dende then tells Goku that the boy is the reincarnation of Kid Buu. Goku has a flashback to him defeating Kid Buu and what he said. Goku says he's too young to participate in the Tournament of Power, but agrees with Dende and looks forward to meeting him.