Experience

Experience is earned by killing monsters and finishing quests. Nothing is yet known of the formulas used in Diablo III, but it's assumed that the process will work roughly as it did in Diablo II.

Gaining Experience

Killing monsters of about the same level as the player will grant them more experience, while monsters are worth a decreasing percentage of their full value as they get further above or below the character's level. Experience is also gained from quests, which are also very likely to be hit with diminishing returns.

Play testers from the beta report reaching level 8 by the time they've completed the beta test, which for many is roughly an hour and fifteen minutes.

Experience Rewards

Experience is often given as a quest reward in Diablo III, and also from events. In previous games experience came only from killing monsters, plus the huge bonus from the Ancients quest in Diablo 2 (and experience penalties on death occurred in higher difficulty levels). In Diablo 3, lots of quest rewards, at least in the early going (which is all anyone outside of Blizzard has gotten to test yet), grant an item and a specific amount of experience. In many early quests, the experience reward is worth many times more than the experience gained from killing the monsters required to finish the quest, making these rewards an essential part of leveling up a character.

Quests are likely to be instrumental to Blizzard when it comes to balancing the leveling curve, particularly since quests can be repeated at the player's leisure.

Maximum Character Level

During most of Diablo III's development, the D3 Team seemed set on repeating Diablo II's maximum level, and they said it would be 99 or 100. That changed during 2010, and in September of that year the developers announced that the maximum level would be... 60.

The design goal in Diablo III is similar to that of World of Warcraft; characters should read the maximum level from clearing out all of the basic content, on the highest difficulty level. This is a big change from Diablo I and Diablo II, where players had to grind through hundreds of boss runs to continue leveling up after they'd finished all the content on Hell difficulty. That was the whole point of the change, according to the developers. In their opinion, giving players nothing else to do but grind the same bosses or areas over and over again is a poor excuse for the end game.

Many players agreed with that logic, but there was still quite a bit of debate over making the maximum level so easy to reach; making it so essentially every character would get to 60. The developers acknowledge that, and have said that the end game and player epeen will be acquired by things other than Clvl. Achievements and Arena rank at least, with perhaps other yet-unannounced features as well.

Skeptical fans also pointed out that Clvl 60 was the same maximum level cap that World of Warcraft offered, before raising that by 10 in each of the first two expansions, and 5 more in the third. Since at least two expansions are planned for Diablo III, that they're planning to enable a higher Clvl cap in the expansions seems fairly obvious, although it has not been confirmed.

Blizzard offered numerous explanations for the change to Clvl 60; see the maximum level article for extensive blue quotes on the matter.

Level Up Bonus

Level up display.

Characters may possibly gain a skill or spell up to level 29, and 5 attribute points (which are automatically distributed) when they level up in Diablo III. Level 10, 20, and 30, the player also unlocks a slot to equip their character with a passive ability.

The actual level up moment is displayed very vividly in Diablo III. Instead of just a sound effect, there's a bright visual graphic, as a funnel of orange light washes down over the player, exploding outwards. Any monsters in range are blasted by the level up bonus, which deals considerable damage. In addition to that, there is a (very) prominent splash graphic that appears over the screen informing the player that they have leveled up, and will also fade in and out with other prompts telling them which skills they have unlocked, if any at all.

Experience Combo Bonuses

A new feature in Diablo III grants experience bonuses for a "Massacre," multiple kills in rapid succession. Characters score the usual experience for each kill, and then get a bonus on top of that for any long series of kills. The player is informed of this bonus by text popping up on the screen whenever a character mows down five or more monsters in a row.

Characters are allowed a few seconds between kills to keep the bonus counting. For instance, if there were a dozen zombies on the screen, at least one needed to go down every 3 or 4 seconds for the bonus to keep adding up. Once there were no kills made for about 5 seconds, the bonus would display in big flashing letters and numbers.

Multiple bonuses could be wracked up in succession; if the aforementioned screen of a dozen zombies yielded 6 quick kills, a pause, and then the other 6, two six-kill combos would be scored. Those would be worth less than a single 12-kill combo, though.

In addition to the massacre combo, there are other ways to gain additional experience through combat. The player may also use the environment against the enemy; springing a trap on monsters within a dungeon or out in the game world will net them a "Pulverize" bonus, and killing multiple monsters with one hit will grant them a mighty blow bonus.

For the pulverize bonus, the monster does not necessarily have to be killed by the environment. The player may finish them off within a short amount of time and still have it count towards the experience bonus.

Due to the nature of these bonuses, it seems highly likely that they will end up being tied to achievements.

Experience bonuses.

In an interview from BlizzCon 2008 [1], Jay Wilson said there was a maximum hard cap for the experience bonus, but that he'd set it so high he didn't think anyone would ever achieve it. Secret Cow Level style mobs would be required?

Q: Is there any caps on the Killing Spree combo?

A: Yes, there is a maximum combination combo. It’s related to your level but I don’t think anyone can actually get it. It has a theoretical limit, but you are not likely to reach it.