Needs review
Source: Dragon Magazine #344

Description: You can harm creatures possessing a mystical connection to your opponent.

Prerequisites: Sneak Attack +3d6, Knowledge (Nature)(1 rank), Knowledge (Arcana)(1 rank)

By reducing your sneak attack damage by two damage dice, you can deal sneak attack damage to a creature linked with your target from a class ability - such as a druid ranger's animal companion, a sorcerer or wizard's familiar, or a paladin's special mount. Only your sneak attack damage (that which remains after subtracting two dice to use this feat) applies, and that damage only affects the target's linked creature - not your target. The base damage of your weapon, your Strength bonus, poison, and similar types of damage do not transfer and apply to your target normally. A creature has a special connection to your target if it gains Hit Dice, hit points, or other abilities due to the target's level. Creatures of a type normally immune to sneak attack damage (such as constructs or undead) are immune to the effects of this feat.