I'm currently playing a level 4 ranger and I'm thinking about multi-classing. I want to know if my animal companion gains a level when I take a level that isn't in Ranger?
Thank you for helping.
It depends on what animal you choose from the classes and how the class ability that give you an animal companion or a mount (or whatever) is written.
Quoting from animal companion:
An animal companion’s abilities are determined by the druid’s level and its animal racial traits.
[...] The druid’s class levels stack with levels of any other classes that are entitled to an animal companion for the purpose of determining the companion’s statistics.
Now, check the classes you are taking. I quote here few examples:
[...] This ability functions like the druid animal companion ability (which is part of the Nature Bond class feature), except that the ranger’s effective druid level is equal to his ranger level –3.
[...] The second option is to form a close bond with an animal companion. A druid may begin play with any of the animals listed in Animal Choices. This animal is a loyal companion that accompanies the druid on her adventures.
In the druid case, ofcourse, there is no explicit state about druid effective level since...well you are a druid so your class levels are druid levels.
A cavalier gains the service of a loyal and trusty steed to carry him into battle. This mount functions as a druid’s animal companion, using the cavalier’s level as his effective druid level. [...]
Now, a game example:
We have a character who is ranger 4/cavalier 4/druid 1...how much strong is his horse animal companion? It's simple!
The ranger states his druid level are equal to his ranger level -3...and since he is a ranger 4 we can say he count as a druid 1 in regard of his animal companion.
The cavalier states he uses all his levels as druid levels in regard to his mount so, in this case, we count as a druid 4 in regard to animal companion.
The druid is the druid so no need to check.
Take all the numbers up we have 1+4+1 and the result is our horse animal companion is a level 6 animal companion (based on druid table ofcourse).
In addiction to all of this here is a faq talking about stacking animal companion levels:
You need to take levels on a class that grants you an animal companion in order to them to level up, as the class abilities that grant an animal companion usually say something along the words:
This ability functions like the druid animal companion ability
Which, in the druid class, says:
Unlike normal animals of its kind, an animal companion’s Hit Dice, abilities, skills, and feats advance as the druid advances in level.
However, that can easily be fixed with the Boon Companion feat:
The abilities of your animal companion or familiar are calculated as though your class were 4 levels higher, to a maximum effective druid level equal to your character level.