Harassment

Harassment is the process of damaging enemy heroes during the laning phase to keep them from farming, to gain lane dominance or to drop their health to prepare for a kill.

Strong harassment can force the enemy to play extremely defensive, spend a lot of gold on consumables, repeatedly return to their base, and miss out on experience and last hits.

Means of harassment
The most basic form of harassment is simply damaging the enemy hero with physical attacks. This is most easily accomplished if your hero is a ranged one (with a greater range allowing for a greater degree of harassment) while the enemy hero or heroes are melee or have low range. Directly attacking an enemy hero will draw creep aggro, which means that nearby enemy creeps will attack you. This can be partly prevented by right-clicking the ground to move into attack range, performing an attack and immediately retreating to avoid being damaged by creeps.

When manually used, castable attack modifiers like Viper's or Huskar's  will not draw creep aggro at all, making them extremely powerful harassment tools.

Also, issuing attack command to enemy from fog and then letting your hero carry out a few attacks while doing nothing and then immediately after 1-2 attacks, a-clicking on an allied creep – one can harrass without drawing aggro. Example video by @D2BOWIE.

Most damaging spells can be used for harassment purposes, and are especially effective because they do not draw creep aggro. Especially suited are slowing abilities like Crystal Maiden's because they allow the user to perform some additional physical attacks on a retreating enemy, as well as spammable abilities with a low mana cost such as Clockwerk's. Experienced players usually integrate this technique into their farming: A well-placed AoE ability can get a last hit on a creep while simultaneously damaging an opponent.

Items that provide some early mana regeneration (e.g., Potions or ) can greatly increase the harassment potential of a hero. Although ranged heroes are generally better suited for physical harassment, an can allow some melee heroes like  to harass effectively.

Countering harassment
Physical harassment should be countered with items that provide health regeneration or armor: A, combined with a can render a hero quite resistant to regular harassment.

Harassment with Spells can be mitigated with a, as they will constantly gain charges and provide the holder with a steady supply of mana and health.

Some abilities are excellent counter-harassment tools. If a player faces heavy harassment, they might consider adapting to a defensive skillbuild, (e.g. investing as many ability points as possible into or ).

Remember that trees block non-flying vision. In the laning stage it can be a good strategy to hide in them and move out only to make a last hit, and then retreat, and repeat.

In some laning situations, it is better to force a small skirmish and attempt to kill an enemy hero instead of just passively allowing the enemy to gain lane dominance through constant harassment. For example, a and  lane will quickly lose the lane against  and  in terms of harassment. However, they have a distinct advantage if they try to kill their opponents instead of just passively laning against them.