This power strengthens all animals you summon, as long as you also have at least 10 ranks in the appropriate summoning power.
If you summon a wolf, it will gain a number of ranks in Feral Senses and Claws of the Wolf equal to your rank in this power, and half that in Regeneration. Your wolf also gains new talents based on your rank: Ambidextrous at rank 1, Razor Claws at rank 5, Cleave at rank 10, Powerful Metabolism at rank 15, Great Cleave at rank 20, Smash at rank 30 and Great Smash at rank 40.
If you summon a swarm of vermin, then your first 10 ranks in this power will each give your swarm +10% health, applied directly after (but separately from) the Endurance talent that all swarms have. Every rank beyond 10 will add +1 Brawn, +1 Mettle, +1 Tenacity and +2 Size to the swarm. The swarm gets a rank in Shapechanging equal to your rank in Beast Master, as well as the following talents: Evasion at rank 5, Cleave at rank 10, House NightWing at rank 20 (but only if you also have it, and they are bats), Venom at rank 30 and Great Cleave at rank 40.