This feat allows spellcasters to acquire a new familiar from a nonstandard list, but only when they could normally acquire a new familiar (see page 52 of the Player’s Handbook).
Prerequisites: Ability to acquire a new familiar, compatible alignment or type/subtype, sufficiently high level (see below).
|Name||Alignment/Type/Subtype||Arcane Spellcaster Level|
|Fiendish Tiny viper snake2||Evil||3rd|
|Air elemental, Small||Air||5th|
|Earth elemental, Small||Earth||5th|
|Fire elemental, Small||Fire||5th|
|Water elemental, Small||Water||5th|
|Formian worker||Lawful neutral||7th|
1 Or other celestial animal from the standard familiar list.
2 Or other fiendish animal from the standard familiar list.
3 The master must first create the homunculus, substituting ichor or another part of the master’s body for blood if necessary.
Benefit: When choosing a familiar, the creatures listed below are also available to the spellcaster. The spellcaster may choose a familiar with an alignment up to one step away on each of the alignment axes (lawful through chaotic, good through evil). For example, a chaotic good spellcaster could acquire a neutral familiar. A lawful neutral spellcaster could acquire a neutral good familiar.
Improved familiars otherwise use the rules on page 52 of the Player’s Handbook, with two exceptions: If the creature’s type is something other than animal, its type does not change; and improved familiars do not gain the ability to speak with other creatures of their kind (although many of them already have the ability to communicate).
The list in the table above presents only a few possible improved familiars. Almost any creature of the same general size and power as those on the list makes a suitable familiar. Nor is the master’s alignment the only possible categorization. For instance, improved familiars could be assigned by the master’s creature type or subtype, as shown above.
Source: Dungeon Master's Guide