Mechanics
Death penalty

When a character dies in Diablo 4, it loses gold and has to backtrack to where it died. Its items lose durability.
Evade ability

The new Evade Ability allows players to dash to safety from dangerous enemy attacks or travel faster.
Lucky Hits

Items with the Lucky Hit attribute have a percentage chance to activate an effect when hitting an enemy.
Mercenaries?

Some Mercenary-like features have been incorporated into the Rogue class, like imbuing elemental damage.
Special movements

Diablo 4 is the first Diablo game that allows characters to climb and jump. Spacebar is the hotkey to do this.
Status effects

Characters and monsters can be granted statuses from items and skills that help or hurt them in battle.
Unstoppable Status

Classes have certain skills that trigger Unstoppable Status, freeing them from Crowd Control effects.
Consumables
Elixirs

Players can receive 30 minute offensive or defensive buffs from Elixirs, and increase Experience gain.
Healing Potions

Diablo 4's Healing system uses Health Potion Charges that are refilled by monster-dropped health globes.
Incense

While in a Party, a player can use Incense to buff the all Party members with a temporary bonus.
Scroll of Escape

Scroll of Escape is a rare drop that teleports a player (often Hardcore) to safety while in danger.
Scrolls

Scrolls play a pivotal role in Hardcore and PvP, getting players out of tough spots -- with unpredictable outcomes.
Detailed & customized characters
Blizzard said that one of its goals with Diablo 4 was to allow each player to create and play the fantasy character that they've always dreamed of, whether that's a big-boned Barbarian with tattoos or a slim-form Necromancer with multiple scars. Diablo 4's character models are extremely detailed, and they'll not only be used in the game, but also in real-time cutscenes. Players can also better track their character's progress, with systems like Challenges (i.e., achievements) and Leaderbards.