Attributes

Attributes are the main statistics of all heroes that independently determine most scaling statistics. These attributes are strength, agility, and intelligence. Attributes are gained when a hero levels up, obtains a talent, buys certain items, or uses certain abilities.

Primary attribute
Every hero has a primary attribute, which controls his or her attack damage. Every point in their primary attribute adds 1 point of damage to their attacks, and any bonus to a hero's primary attribute will affect that hero's attack damage. Usually, a hero's primary attribute will determine how he or she is played. For example, intelligence heroes are typically more dependent on abilities. A hero's primary attribute typically grows faster than the other two attributes.

Strength
Strength is a measure of a hero's toughness and endurance. Strength determines a hero's maximum health and health regeneration. Heroes with strength as their primary attribute can be hard to kill, so they will often take initiator and tank roles, initiating fights and taking most of the damage from enemy attacks.
 * Every point in strength increases maximum health by 20.
 * Every point in strength increases health regeneration by 0.03 HP per second.
 * If strength is a hero's primary attribute, every point in strength increases his or her attack damage by 1.

Agility
Agility is a measure of a hero's swiftness and dexterity. Agility determines a hero's armor and attack speed. Heroes with agility as their primary attribute tend to be more dependent on their auto-attacks and items, and are usually capable of falling back on their abilities in a pinch. Agility heroes often take carry and Gank roles.
 * Every point in agility increases a hero's armor by 1/7.
 * Every point in agility increases a hero's attack speed by 1.
 * If agility is a hero's primary attribute, every point in agility increases his or her attack damage by 1.

Intelligence
Intelligence is a measure of a hero's wit and wisdom. Intelligence determines a hero's maximum mana, mana regeneration and spell damage. Heroes with intelligence as their primary attribute tend to rely on their abilities to deal damage or help others. Intelligence heroes often take support, gank, and pusher roles.
 * Every point in intelligence increases a hero's maximum Mana by 12.
 * Every point in intelligence increases a hero's mana regeneration by 0.04 mana per second.
 * Every point in intelligence increases a hero's spell damage by 0.0625%.
 * If intelligence is a hero's primary attribute, every point in intelligence increases his or her attack damage by 1.

Items improving attributes
Each attribute has its own set of items that focus on boosting it. These items are different for each attribute. In order to categorize them, they're split into 5 different sections:
 * Simple Items boost their associated attribute by 3. These items can be built into their Upgrade Item, and are usually taken as starting items to make up for gaps in a hero's statistics. The Iron Branch costs 50 gold while the other 3 cost 150 gold.
 * Upgrade Items boost their associated attribute by 6, the other two attributes by 3, and increase damage by 3. They are made by combining an attribute's Simple Item, a Circlet, and a recipe. They're generally taken if a hero is having difficulty reaching their core items. Their costs differ between attributes.
 * Medium Items boost their associated attribute by 6. Though generally not taken to increase attributes, these items can all be combined with Boots of Speed and Gloves of Haste in order to build Power Treads. They cost 450 gold.
 * Large Items boost their associated attribute by 10. These items are usually components in more powerful items, and all combined with Point Booster are used to make Aghanim's Scepter. They cost 1000 gold.
 * Ultimate Items boost their associated attribute by 25. These are mostly used to make late game items because of how expensive they are. Their costs differ between attributes, but are between 2700 and 3200 gold.

Abilities modified by attributes

 * Illusions benefit from attributes.