[BENIGN]
Determines whether creature
can show up on "tame" maps (includes elephants), which will generally avoid dwarves, although they
may chase and/or attack them if they get too close. (in other words they just prefer to be left alone
Source:
http://df.magmawiki.com/index.php/Creature_token#ixzz0wzgY9XxGIt may actually limit it to benign areas, like the savages token does. These tokens and the [GOOD] and [EVIL] ones don't affect the creatures' reactions to one another and you, just restrict them to certain biomes. Currently all animals seem to be neutral until provoked at least, and unspeakably cruel to anything they set eyes on at most. the beastmen tribes are an entity anyway, so this won't affect their hostility in the first place.
There really isn't an entity token that controls a civilization's feelings towards your dwarves except the ethics tags, which, (along with the biome and location tags) according to Toady's comments in the entity_default file, currently do nothing on layer_linked civs, like the beastman civs. They'll be hostile by default until he changes this, and there doesn't seem to be a way to keep them underground while also letting them use the ethics and location tags. You can put them in caves like kobolds, but that's as close as you can get.