Cutscene

Cutscenes or Cinematics are points in the Diablo series where a special event takes place in which requires a short movie to better explain or heighten interest in a coming event.

Diablo I
The few cutscenes in Diablo I were basically used to show forthcoming battles. There were only two cutscenes included in the final game.

The first was a cutscene showing the Archbishop Lazarus at the Tristram Cathedral's altar, obviously possessed by Diablo. This led to the player's confrontation with Lazarus and his succubus guards.

In the second and final cutscene, it shows Diablo's death as his body crumbles to ash and the young Prince Albrecht is released from his torment. Also in the scene, the character is shown stabbing himself in the forehead with the Soulstone in order to contain Diablo's evil. This scene is notable because originally, all three character classes had their own version of this scene, but the final version of the game only contained the Warrior's scene, further reinforcing the fact that the Dark Wanderer is in fact, the Warrior from Diablo I.

A ending scene shows the Dark Wanderer as his fate is explained by a narrator.

Deleted scenes

 * Upon entering the lair of the Butcher in the Cathedral, a cinematic was to be shown of him hacking the body of a dead villager and hooking it onto the wall. Sadly, this was never placed into the final game. Although it can be seen in Diablo Spawn - a demo of the game. The clip can be viewed here:
 * The other removed cutscene was the one of Diablo gaining power if the hero failed the Map of the Stars quest. It was removed because the quest itself was taken out of the game, as the developers felt that it ruined the player-driven nature of the game.

Diablo: Hellfire
The Hellfire expansion for Diablo came with a new cinematic, related to Na-Krul. It depicted Na-Krul being summoned into Sanctuary.

Diablo II

 * see also The Calling released in 1999

Diablo II took cutscenes to a new level, with improved graphics and showing more interest in revealing the storyline. At the beginning of each Act, the narrator, a crazed old man named Marius, tells Baal (believing him to be Tyrael), why he was unable to complete the task of bringing the Soulstone of Baal to the Hellforge to be destroyed.

Diablo II: Lord of Destruction
The Lord of Destruction expansion brought two more cutscenes to the sequel, both of which were praised highly for their quality and content in many game reviews.

The first epic scene showed Baal, now in his true form with the powers of his Soulstone, and the Demonic Legion invading Mount Arreat. Their ascent is hurdled at the gates of the Capital, Sescheron, by an old, but brave Barbarian guard. The guard tries to convince Baal to turn back, lest the Barbarian Hordes within the city obliterate the Legion. Baal thinks about the proposal and proceeds to literally explode the guard as his reply with his Mana Rift spell. Then, the Legion pours into the gates hacking away at all who stand in their way.

The final cutscene featured the enigmatic Archangel Tyrael, dressed in a new garb and spectacular wing effects, trying to save Sanctuary from the Worldstone's corruption by destroying it. This cutscene may play a huge part in deciding the storyline of Diablo III. The music and direction of this scene has been lauded by fans and critics alike. The expansion ends in a cliff-hanger, like all the previous releases.

Diablo III
There are five cinematics in Diablo III: Two more were added in Reaper of Souls: Majority of interludes between quests are given in form of engine-based cinematics. Class intros and some cinematics between quests are given in form of animated sketches and narrated by the player character's voice.
 * Introduction: arrival of the Fallen Star and disappearance of Deckard Cain
 * Three Act transitions:
 * After : Tyrael showing Leah his sacrifice at the Cain's funeral
 * After : Leah's vision of Azmodan through the Black Soulstone
 * After : Diablo arriving to High Heavens, defeating Imperius and shattering Diamond Gates
 * Ending: Diablo's body crumbling into dust, and High Heavens restoring as Tyrael is chosen the new Aspect of Wisdom
 * Introduction: Malthael taking the Black Soulstone
 * Ending: The Nephalem, Imperius and Tyrael witnessing Malthael's defeat

For a complete list list of Diablo III videos and trailers, see Diablo III videos.