Initiating

Initiating is the capability of Heroes to cripple a group of enemies before a clash to gain an upper hand. The concept of initiating is central to success at the mid-and late game phase of any game of Dota, and mainly deals with the art of starting a teamfight in such a way that your team already is advantaged when the fight begins. In a team without heroes well suited to this task, each Teamfight could become a messy affair, or your team runs the risk of always getting attacked first.

Heroes
Initiators are the most important driving force in winning team clashes. Most Initiators have an area skill/s that delivers heavy damage and/or severe crowd control status effects to multiple enemy heroes. Initiators generally double as a Tank, Support, or Roamer. Some Initiators focus more on damaging singular targets to help eliminate them, usually the enemy Carry.

Be aware that playing an Initiator requires one to be bold and to be aware of the intentions of one's team. Should one initiate, one's team must be able to commit.

Heroes whose primary function is Initiation are Tidehunter,  Earthshaker,  Sand King,  Clockwerk,  Axe,  Enigma, and  Vengeful Spirit. The full list of heroes with initiative capabilities is below.

Items
Items really depend on what type of Initiator one could be. If their initiating skill requires them to be close such as Earthshaker's Echo Slam and Tidehunter's Ravage, an item such as Blink Dagger, Force Staff, or even Shadow Blade can really ease the job. If their initiating skill requires them to be uninterrupted throughout the battle such as Sand King's Epicenter or Crystal Maiden's Freezing Field, Black King Bar allows them to to remain active throughout the clash for them to deliver the most out of everything. Initiators also need to disable the most amount of enemies at one time, so Eul's Scepter of Divinity and Scythe of Vyse are also great items. Area debuff items such as Shiva's Guard and Assault Cuirass also greatly help. Initiators also make great carriers of area support items such as Mekansm and Pipe of Insight. Items that increase survivability such as Heart of Tarrasque and Blade Mail also work.

The Key to Initiating
There are many, many ways to handle a good initiation, but often, the ingredient is a hero with a Blink Dagger and a game-changing AOE disable, a warded map, and a very good sense of intuition and map awareness.There are several ways to initiate: Either catch the other team while they are badly positioned, at a time when your own teammates are ready to pounce on them, or isolate and immediately kill one enemy, then mop up the rest when they clump up to try to defend him.

Being the Initiator means that you are basically in charge of aggression for your team. However, some heroes who are commonly labelled as Initiators (Sand King, Earthshaker, Enigma) are equally good at immediately winning a team fight that is already underway, because the other team might be loathe to clump themselves together under the threat of huge aoe damage until they have an opportunity to actually attack the other team.

Essentially, initiation is about disabling as much of the enemy as possible so that they cannot escape when your team starts assaulting the enemy. To achieve this easier, it is recommended that you have the means to catch the enemy by surprise by appearing in their midst unexpectedly. This allows you to land your AOE disable, since the enemy will have hardly any time to react. To surprise the enemy, oftentimes a Blink Dagger is used so that they have as little time to react as possible. If not, a or an Rune of Invisibility can be used, but as this can be countered with a  it is not as good. Alternatively, if you have a skill that can stun a large area from afar, such as Tiny's Avalanche, Warlock's Chaotic Offering, or Leshrac's Split Earth, you can consider simply charging at your opponent and launching your stun, but beware that the opponent will have stunners too, and that a fraction of a second's slowness in casting could mean you getting stunned and them pulling off a successful initiation. In Dota, teamfights can be won in mere seconds, so one misstep could cost you a lot.

Heroes that can deal high AOE damage can also be considered initiators, because they force the enemy to scatter, and in some rare cases, flee (for example a well-used Echo Stomp could slash a whole team's HP in half). In this case, the enemy will try to escape, and that is a prime opportunity or your team to charge in and massacre them all.

It is best to initiate at a place where the enemy cannot spread out. The goal of a teamfight is to eliminate as many of the opponent Heroes as possible, and so if you were to initiate in an open area, you could have many heroes going in many different directions. This limits the effectiveness of your follow-up Nukers' spells and makes it harder to wipe-out the enemy team (the most desired outcome of any teamfight).

Also, as mentioned at the start of this section, GOOD WARDING is imperative. Without detailed vision of the map, it becomes hard to know if that lone hero is merely bait for a teamfight you will not initiate. It becomes hard to know where exactly you should set your trap, and whether you can rush there in time to set up (the initiators' back-ups' positioning is vital).

"Strike when your enemy is most vulnerable." This is the basic principle that initiation will fulfill: your AOE disable will make the enemy vulnerable, and what's left is to have fun mopping up the foe.