Changes from DotA

DotA, or Defense of the Ancients, was a custom map created for the Blizzard game, Warcraft 3 and Warcraft 3: The Frozen Throne. It borrowed many elements from the game and was based on its engine. Dota 2 is a complete game created by Valve on the Source Engine, however, and many differences exist due to copyright concerns and previous engine-related bugs.

Misc. Changes

 * Quelling Blade is not limited to only one and will stack.
 * You can resell items within the first ten seconds for full price.
 * Bottle can be filled with another rune even when full.
 * A Bottle with a rune in it is no longer a shareable item.
 * AI practice bots
 * Manabars on allies
 * Crystal Maiden's Frostbite cannot freeze the enemy's fountain
 * Crystal Maiden's Frostbite works on Batrider using firefly
 * Fountain cannot be attacked
 * Hotkeys are customizable
 * Phase Boots do not prevent Skull Basher, Monkey King Bar, or items that grant Critical Strike from procing
 * Skills can be leveled up while dead.
 * Hero can no longer be deselected (except for selecting other controllable units, such as Couriers or pets)
 * Item shops are condensed (there are now only the main shop, side shop, and secret shops)
 * Quelling Blade now works with Orb Effects.
 * Control Groups now save between summons for summoned minions (even when they die)
 * Cooldowns on abilities now show time left in seconds.
 * Items and many heroes have entirely new lore.
 * Mjollnir/Maelstrom currently stack with other Orb Effects, overriding them on proc
 * Orb of Venom is now an Orb Effect
 * Eye of Skadi (both ranged and melee versions) will now work with items that grant Lifesteal, but are both Orb Effects.

Items
Due to copyright concerns, some items in Dota 2 have different names from their DotaA equivalent.


 * Lothar's Edge is now Shadow Blade
 * Buriza-do kyanon is now Daedalus
 * Sobi Mask is now Sage's Mask
 * Ancient Janggo of Endurance is now Drum of Endurance
 * Kelen's Dagger is now Blink Dagger
 * Mask of Death is now Morbid Mask
 * Nathrazim Buckler is now Buckler
 * Khadgar's Pipe of Insight is now Pipe of Insight
 * Cranium Basher is now Skull Basher
 * Eaglehorn is now Eaglesong
 * Guinsoo's Scythe of Vyse is now Scythe of Vyse

Heroes

 * Nerubian Assassin is now Nyx Assassin
 * Alleria the Windrunner is now Lyralei the Windrunner
 * Leoric the Skeleton King is now Ostarion the Skeleton King
 * Kael the Invoker is now Garrol the Invoker
 * Rexxar the Beastmaster is now Karroch the Beastmaster
 * Anub'seran the Nerubian Weaver is now Skitskurr the Weaver
 * Furion the Prophet is now Tequoia the Nature's Prophet
 * Dwarven Sniper is now Sniper
 * Clockwerk Goblin is now Clockwerk
 * Kel'thuzad the Lich is now Ethreain the Lich
 * Vol'jinn the Witch Doctor is now Zharvakko the Witch Doctor

Buff Placers
Buff Placers refer to a group of Items in DotA that applied a buff to a Hero's attacks. Typically, they were also Orb Effects. Unlike Orb Effects, which do not stack for balance reasons, the Warcraft 3 engine was limited in that it only allowed one buff to be applied per attack. This meant that Buff Placers did not stack. In Dota 2, however, Buff Placers will now stack with each other. For example, Venomancer's Poison Sting will now stack with Desolator, even though both of them were Buff Placers in DotA.