well, you said the bond was important, and so was instinct, and that the rescuer used claws and fangs and such to do away with the baddies.
But the rescuer doesn't become any kind of creature, or summon any creature? And his power isn't Critter Instinct, or Berserker Instinct? Or Reincarnation 5: Soul Link...
curiouser and curiouser...
“…Judge not what a man has done, but judge what he could have done if he was a different bloke altogether. For art thou a leper? And a leper can changeth his spots…” --Rudy Wade, Misfits (Series 4, Episode 8)