Companions are the "pets" of Swtor and every class not only has access to a companion but they are almost a requirement to play the game. As you could have already guessed companions follow you everywhere and benefit you many different ways, one of those ways by helping you fight in combat. But that's not all. In Swtor companions play a major role throughout the game by being the only way players can participate in the "crew skills" system that Bioware has in place.
For those still uinfamiliar with Swtor, Crew Skills is pretty much the general blanket term for all Tradeskills currently in the game. In Swtor players are able to have their companions craft items for them when they are not around, have their companions gather items for them and even send their companions on missions. All three of these things that your companions are able to do can be done while the player is online or offline, it doesn't even matter!
The way Bioware has the Crew Skills system set up is quite interesting and is one of the most unqiue things I have come across when playing an MMORPG. The concept of being able to send your companions out on missions to gather items for you when you're no where even near them is just plain awesome. Now that you know the general idea behind companions and how they affect your game it is time to go into more detail.
There are many different Crew Skills in the game, as I am sure you already know by now... Crew Skills are the Professions or Tradeskills, whichever word you prefer, of Swtor. Unlike any other game in order to participate in any of the Crew Skills you will need to have a Companion. Players can gather on their own but they are not able to run missions or able to craft without a companion.
That means while you will be able to participate in Archaeology, Bioanalysis, Scavenging and Slicing other crafting Crew Skills such as Armormech, Armstech, Artifice, Biochem, Cybertech and Synthweaving will be off limits unless you have a companion available to you. Also the mission Crew Skills, Diplomacy, Investigation, Treasure Hunting and Underworld Trading will also be off limits unless you have a companion available to you.
For gathering Crew Skills you are able to raise them the old fashion way, such as going around and collecting all the different nodes or you can raise them just like they were Mission Skills, by running different types of missions for skill ups. If you're interested in running Missions on any of the Crew Skills take a look at this guide to learn more.
The final thing worth mentioning about Companions and Crew Skills is each companion for every class will have different and unique bonuses available to them for different Crew Skills. These bonuses can be something simple such as +15 Bioanalysis or Archaeology to something more unqiue and useful such as +2 Critical chance with Underworld Trading. If you're interested in seeing the long list of bonuses available to each companion take a look at this guide here.
Besides being useful in crafting items and gathering materials for you, companions play a major role in the game's combat system. They play such an important role that an entire attribute (Presence) is dedicated to improving how much health and damage amongst other things your companion does. Companions are so important in the game that once you get up to a certain level it will be almost impossible for you to kill anything without one.
In addition to dealing damage for you and helping you fight, certain important PvE abilities require companions to use. These abilities are mainly here to assist you in completing the harder bosses throughout the story and trust me, you will be using them a ton! One of the abilties that you get early on increases your health by 1% a tick (heals you in other words) and also refreshes one of you most important abilities. The abillity it refreshes changes depending on your class but for all classes I can guarantee you that it is an extremely important ability.
There is another ability you get that requires a companion that decreases the damage taken by you and your companion by 50% for 15 seconds. You don't get this ability until much later on but with this ability and the one aforementioned gold star mobs stand almost zero chance against you.
Probably the thing people are most curious about is what companions are available to each class and how many companions can you have. Players are able to have a total of 6 companions, 5 of them being unique and one being the droid that comes with your ship in the beginning of the game. You get these companions slowly throughout the game as you level up and complete the Class Story quests.
Most classes have two companions before leaving their home planet (either Coruscant for Republic or Dromund Kaas for Imperials) and then they get the ship droid at level 16 or whatever level it is they exit the planet. Many of you may already have found out that depending on your level and how many companions you have available determines how many companions you can have out on Crew Missions at a single time.
I've found that at level 20 you can have two companions out, 30 you can have 3, 40 you can have 4 and at level 50 you can have all but a single companion out at once. The number doesn't increase exactly at those levels but they are rough ranges for when the amount of companions you can send out goes up. But anyway without further ado, here is the long giant list of all the companions you can have!
Bounty Hunter Companions
Imperial Agent Companions
Sith Inquisitor Companions
Sith Warrior Companions
Jedi Consular Companions
Jedi Knight Companions