Familiars in BG2

          Once again, the rules: Only your main character can cast Find Familiar, and then only if your character has access to Wizard spells. If your Familiar dies, you may cast the spell again to get a replacement, but you may not have more than 1 Familiar at the same time. Note that when your Familiar is out on its own, it could potentially get lost when the party moves from one area to another, and you will not be able to summon another one. There is also a chance of losing your Familiar when it's safely riding in your pack: If a non-party NPC gives you an item, it could possibly displace an item you were already carrying, knocking it to the ground. In each case, it is possible to return to the area where you lost your Familiar, and get it back.
          Most Familiars have 24 hitpoints—when you summon your Familiar, your maximum hitpoints will increase by an amount equal to half of your Familiar's. Upon starting the ToB portion of BG2, all Familiars get a boost to all of their stats; nowhere near enough to make them actually useful for anything resembling combat, but then that's not really a surprise. When your Familiar is out of your pack, you can talk to it—it's not a scintillating conversational companion, but you can pet it or punish it if you want to. This is also how you get items that your Familiar has pickpocketed. Make sure to heal your Familiar if necessary. Some of the Familiars can Detect Traps, but they cannot Disarm them. All Familiars can be used for exploration: Their line of sight does not stop (as Summoned creatures' do) at the maximum sight range of the nearest party member. All their attacks strike as Normal weapons, and they are immune to Sleep/Unconsciousness, Petrification, and Level Drain.

Which Familiar you will get is determined by your PC's Alignment, as follows:

Ali.FamiliarSoAToB
LG,
NG
Psuedo Dragon
24 hp, AC=-2, THAC0=13, ApR=2, 1D3 Piercing+chance of Sleep. 50% Magic Resistance. Can cast Blur 1x/day. Regenerates 1hp/round. 48hp, AC=-2, THAC0=8, ApR=2, 1D6 Piercing+chance of Sleep. 50% Magic Resistance, Can cast Blur & Ghost Armor 1x/day, & Detect Illusion 2x/day. Regenerates 1hp/round.
CG
Fairy Dragon
24 hp, AC=4, THAC0=17, ApR=2, 1D2 Slashing. 32% Magic Resistance. Can cast Mirror Image and Invisibility 10' Radius, each 1x/day. 48 hp, AC=0, THAC0=12, ApR=2, 1D2 Slashing. 45% Magic Resistance. Can cast Mirror Image and Invisibility 10' Radius, each 1x/day.
LN
Ferret
24 hp, AC=0, THAC0=17, ApR=2, 1D3 Slashing. 50% magic resistance, 75% Pick Pockets, 20% Find Traps, 40% Stealth. 48 hp, AC=-4, THAC0=12, ApR=2, 1D6 Slashing. 65% Magic Resistance. 95% Pick Pockets, 60% Stealth & Find Traps.
CN
Rabbit
24 hp, AC=1, THAC0=17, ApR=2, 1D2 Slashing. Resistances: 65% Magic, 75% Cold/Fire/Electricity. 30% Stealth, 50% Find Traps. 48 hp, AC=1, THAC0=12, ApR=2, 1D2 Slashing. Resistances: 65% Magic, 75% Cold/Fire/Electricity. 60% Stealth, 85% Find Traps, 50% Detect Illusions.
CN
Cat
24 hp, AC=0, THAC0=17, ApR=2, 1D3 Slashing. 50% magic resistance, 30% Pick Pockets, 99% Stealth. 48 hp, AC=-4, THAC0=12, ApR=2, 1D3 Slashing. 65% Magic Resistance, 60% Pick Pockets, Find Traps, & Detect Illusions, 99% Stealth.
LE
Imp
18 hp, AC=2, THAC0=19, ApR=1, 1D6 Piercing+chance of Poison. Resistances: 25% Magic, 100% Cold/Electricity/Fire. Can cast Polymorph Other 1x/day. Regenerates 1hp/round. 48 hp, AC=-2, THAC0=12, ApR=2, 1D6 Piercing+chance of Poison. Resistances: 35% Magic, 100% Cold/Electricity/Fire. Can cast Polymorph Other 1x/day. Regenerates 1hp/round.
NE
Dust Mephit
24 hp, AC=6, THAC0=17, ApR=2, 1D2+1 Slashing. Resistances: 10% Magic, 50% Slashing/Piercing/Missile, 100% Fire. Can cast Glitterdust 1x/day & Glass Dust 2x/day. Regenerates 1hp/round. 48 hp, AC=3, THAC0=14, ApR=2, 1D3+1 Slashing. Resistances: 25% Magic, 60% Slashing/Piercing/Missile, 100% Fire. Can cast Glitterdust 1x/day & Glass Dust 2x/day. Regenerates 1hp/sec.
CE
Quasit
24 hp, AC=2, THAC0=17, ApR=3, 1D6 Slashing. Resistances: 25% Magic, 100% Cold/Electricity/Fire. Can cast Blur & Horror each 1x/day. Regenerates 1hp/round. 48 hp, AC=-2, THAC0=12, ApR=3, 1D6 Piercing+chance of draining 1 point of DEX. Resistances: 35% Magic, 100% Cold/Electricity/Fire. Can cast Blur & Horror each 1x/day. Regenerates 1hp/round.