Familiars and Animal Companions are quite useful. They are similar to summoning spells, except are more permanent; the allies they summon stick around indefinitely, and they are more tactically useful than many of the other summons in Neverwinter Nights. Usual vault rules apply for my FAQs: If you post any of the contents, give credit where credit is due, or I'll track you down, splatter you with ketchup, torture you, and eventually devour you. You have been warned.
So anyway. To begin: How are Familiars and Companions different from regular summons? Well.....
How Familiars and Animal Companions differ from normal summons:
1. Easily healable. Feed them when they've lost hit points, and *Sproing!* They're back to full HP. sadly, you can't do this in the middle of a battle, but it can easily prolong the life of a Familiar or Animal Companion.
2. Free to summon. They take up no slots, are easily called, and only take a standard action to bring out.
3. You can name them.
4. If they die, it isn't a big deal, because you can just re-summon them.
5. They have an indefinite timespan, so once they are summoned, they stick with you, regardless of how much time elapses. They will rest when you do, and recover their abilities when you do.
6. Wide array of special abilities. All of them offers a unique ability or two.
7. Don't take up a summoned creature slot. You can summon a Familiar or Animal Companion, then summon something else up.
8. Can be summoned at the same time. You can have both a Familiar and Animal Companion out, and roaming around with you. And you can still summon creatures. Which is hilarious, because I've had Ivy being followed around by a Dire Badger, Her Familiar, and her Animal Companion.
Which Familiar or Companion is right for you? Well, to ease your decisions, here's a complete guide to them. With this, you'll be better-able to choose a familiar based on your combat style and abilities.
Familiars are obtained by Wizards and Sorcerers. In general, Familiars are poor combatants, but make up for this by having an enormous range of abilities and in some cases, spellcasting or spell-like abilities. Correctly used, Familiars are wonderful companions that should be used at every opportunity. In addition, unlike Animal Companions, Familiars can be possessed - you can control their actions. This is very useful for scouting around, opening doors, and setting off traps (sick, but sometimes necessary).
The following are the available familiars and their abilities:
Bat: Bats are kinda nifty as far as familiars go. They gain damage reduction, and do so early, so they tend to fare better, early-game, then other Familiars. However, they have rather poor damage reduction, so this ability loses its impact very quickly. Where the Bat does excel is having an array of fear-affect abilities that get stronger with the master's level. Fear is quite a nice status ailment, and the Bat is one of the few Familiars and Companions with an ability that causes it. Even niftier, the Bat has both a fear gaze, AND a fear howl. The bat's bite does poor damage, however, which limits its utility as a combat Familiar.
Panther: The Panther is about as close to a frontline combat creature as a Familiar can get. It gets levels of Rogue, so it quickly gets Evasion, and can make sneak attacks - very nice for a more martial spellcaster. This combines to make the Panther a very nice backup familiar. It's also capable of pulling its weight in combat with only a little extra effort. Unfortunately, the Panther is also the biggest Familiar and is one of the easiest to hit as a result.
Hell Hound: The Hell Hound has a ton of skills, and is half-decent in combat to boot. Its cone of fire ability is quite powerful, but only gets 2 shots at the highest level. Its major advantage is the fact that it has a broad array of skills; the Hell Hound can act as a second set of eyes and ears, and will often have better listen and spot modifiers then you do. This can help you sniff out secret doors. As an Outsider, it's immune to a lot of things that you aren't, including domination spells. The Hell Hound also has Scent, which lets it sniff out invisible creatures as well. If you're considering a Familiar that can do a lot of different things, lean in this direction.
Imp: One of the main support Familiars. Its major advantage is that every attack it makes is poisoned, thus allowing it to do ability damage to enemies. Its poison deals constitution damage, which adversely affects the enemy's saves and hit points. Spellcasters who use a lot of spells relying on Fortitude (especially insta-kill casters and Horrid Wilting users) should seriously consider using the Imp. The Imp's invisibility spell, at a glance, sort of sucks, but has an advantage a lot of people miss - he can cast it on you, too!
Fire Mephit: This is a support familiar that gets some light Damage Reduction, too. The main advantage of the Fire Mephit is that its Fire Bolt ability deals a good chunk of damage from such a small creature. The Fire Mephit is reasonably capable in melee, but it becomes less useful when it's exhausted its supply of Fire Bolts. Nonetheless, a useful familiar.
Ice Mephit: Well, shit. This guy's exactly like his brother! Actually, the Ice Mephit has slightly better stats, too. Like the Fire Mephit, The Ice Mephit's primary advantage is that its Ice Bolt ability deals a good chunk of damage from such a small creature. Like the Fire Mephit, it also has weak Damage Reduction. The Ice Mephit deals ice damage, however, so whilst it has a better statline then the Fire Mephit, more creatures resist ice. A very popular familiar.
Pixie: The Pixie is like the Panther, but gets a hell of a lot more skills. It's not nearly as good in combat, but it relies on sneak attacks for damage, so this is not an issue. Where the Pixie excels is that it can do a lot of tasks a Rogue can - including picking locks, clicking switches, and disarming traps! This makes the Pixie a very nice Familiar for those adventurers who lack a Rogue. In addition, the Pixie can help you hide, too - she can cast Invisibility, and fully upgraded, can cast it a lot. She's also really tiny and hard to hit. A word of note: My friend Dave has accidentally killed his Pixie familiar on hardcore difficulty more times then we can count - when we lost track, it was somewhere around 90. A highly useful familiar.
Raven: The Raven is OK, but it is still arguably the weakest familiar in NWN. It deals poor damage, but it gets a very large number of skills and can be an excellent scout or support Familiar. It also has an impressive amount of hit points for such a small creature; A Raven can be fairly hard to kill at high levels (though admittedly, it starts small). Though certainly it has a charm all its own to it (And it gets a huge advantage with the few skills it has), the Raven is something of a bust when it comes to actual combat.
Faerie Dragon: This is a very popular and useful Familiar. The Faerie Dragon is decent in combat, but more importantly, boasts an array of support abilities, including a magic bolt attack (that causes Daze status), a confusion breath weapon, and the ability to cast Improved Invisibility. As a dragon, it gets a host of innate immunities, including to paralysis and sleep. It also gets Improved Evasion very, very early on. It's hard to recommend a Familiar as much as this one; it has a lot of strengths and very few vulnerabilities to speak of.
Pseudodragon: The Familiar bad boy of close combat. The Pseudodragon gets an impressive array of abilities, including a poisoned stinger and a breath weapon that duplicates a Burning Hands spell. The major advantage of the Pseudodragon familiar is that it can be quite useful in combat despite low stats; it's hard to recommend a better familiar for direct combat, due to its unique array of special attacks, immunities, and resistances. The poison sting it has never gets stronger, however, so it quickly becomes nearly useless (but it still does damage, and enemies may still get poisoned if they roll badly). Overall, a damned good familiar with relatively few drawbacks.
Eyeball: The Eyeball is extremely difficult for those unfamiliar with it to gauge, because the programmers foolishly left out the list of what exactly it can do. Truth be told, the Eyeball is possibly the best ranged attacker of all the Familiars. It has 4 rays, including one that inflicts fire damage, one that inflicts ice damage, one which duplicates an Inflict Wounds spell, and one that causes daze. These all get stronger (and can be used more times per day) with level. In addition, the Eyeball has possibly the best Spot modifier of any Familiar in the game. Presumably, this is due to its multiple eyes. It also looks kinda cool. The Eyeball is well-suited to backing up its master by assisting his/her spellcasting with rays from its eyes. Unfortunately, the Eyeball has kinda poor defense, and deals only light damage in melee.
Animal Companions are like familiars, but... They're animals. Druids and Rangers get Animal Companions. Animal Companions are much better suited to melee combat then their counterparts, and have both better hit points and better defense, but they also use much more direct means in combat - don't expect your companion to breathe fire or shoot beams of magic - they're far more likely to just run over and start kicking ass. Like the Familiars, they should be used at every opportunity. An Animal Companion benefits from several Just-for-Companions spells and items - things like the Branch of Giving, Greater Magic Fang, and Bull's Strength turns any companion into a veritable killing machine in melee!
The following are the available Animal Companions, and their abilities:
Badger: The Badger is small, doesn't deal much damage, and is kinda funny to laugh at, but is nonetheless quite vicious, especially with a sufficiently strong Druid or Ranger at the helm. The Badger is a combat familiar, but one never really realizes that until you see the Badger's skills and abilities. It gets the ability to Rage, like a Barbarian. This kicks its strength up to respectable levels and will give it a ton of hit points for such a small creature. The Badger is ideal for tricking opponents; people expecting a weak enemy will be horrified when the little thing rages and starts dealing more than 4 times the damage it was before. Though certainly not the best familiar, it's arguably not the worst, either.
Wolf: The wolf is stealthy, brave, a good fighter, and gets a nifty ability - it can howl and terrify enemies. It gets more uses of this as the master levels up, and the fact that it can hide and then strike without warning makes it a very effective fighter. It also can deal reasonable damage in Melee. The Wolf is a very common companion, and very popular, with good reason; It's excellent overall.
Brown Bear: Sometimes, subtlety takes a back seat, and you're forced to paint in broad, explosive strokes. For these occasions, the Brown Bear makes the call. The Bear is all about combat; it's big and powerful enough to soak up a ton of damage whilst kicking out a ton of punishment in melee. This thing is a favorite among offensive spellcasting Druids, who kick back and cast spells whilst their buffed-up Brown Bear wanders into melee and starts maiming things. Unfortunately, combat is pretty much all the damned thing is good at. The Bear has the most HP of any animal companion - at high levels, it can have a ridiculous amount.
Boar: The Boar is a more graceful alternative to the Brown Bear and Dire Wolf - it has less hit points, and deals less damage, but it has better skills and a nifty special ability. The Boar gets Ferocity, which gives it a big advantage - it can deal more damage faster. The Boar is quite deadly in close combat, especially when buffed-up. It also gets an impressive amount of HP, though not on level with the Dire Wolf or Brown Bear.
Hawk: The Hawk is pretty damned good. It's strong enough to deal damage in melee, and it can disarm opponents, which is highly useful in and of itself. As it levels up, it gets evasion and several other skills. It also has by far the best Spot modifier of all the animal companions. It also has a good AC and does not provoke attacks of opportunity when flying around the battlefield. A very useful companion overall.
Panther: Whoa, deja vu. The Panther is one of only 2 Companions that gets levels of Rogue, and thus, it can make sneak attacks - which are extremely useful. As stated, it's also quite capable of pulling its weight in combat. Unfortunately, its skills are very limited when compared to other companions.
Giant Spider: OK, this thing is pretty damned good. Giant Spiders get a poisonous bite that gets stronger as the master levels up, and it gets the ability to cast Web, too! They also deal reasonable damage in melee, and being vermin, are immune to mind-affecting abilities. Giant Spiders rock in combat, and are also fairly good scouts - they're highly recommended for a wide array of roles and are arguably the most flexible Companion. It does have a somewhat low HP level however, so it cannot take a terribly large amount of abuse. A favorite of Dark_Priest.
Dire Wolf: The Dire Wolf is very similar to the Brown Bear, but has a higher strength level in exchange for having lower hit points. This actually makes it somewhat more suitable to frontline combat then the Bear, though it does not soak up damage quite as well as its counterpart. The Dire Wolf is probably the best melee fighter of all the Animal Companions, owing to its high strength.
Dire Rat: Many genuinely like the Dire Rat. It gets levels of Rogue, and thus can make sneak attacks, but backs this ability up with a disease-bearing bite that can really mess the enemy up if used for hit-and-run attacks. The disease the Dire Rat carries may actually run its course during combat - if it does, your enemies are likely to be in sorry shape. Unfortunately, the Dire Rat is squarely average in combat and in virtually all other aspects, and the disease takes time to take effect. Correctly used, however, it can soften an enemy up for an attack, or weaken them enough so that they're easy to finish off.
Hope that helped, Peeps. Peace out.