D&Dtools1

Benefit

When you use a spell or spell-like ability to summon a creature native to a plane that has a planar touchstone site to which you have forged a link (see the Planar Touchstone feat), you imbue the creature with exceptional resilience. The creature gains a +4 bonus to its Armor Class and on saving throws for the duration of the summoning effect. Furthermore, the duration of the summoning effect that brought the creature is doubled. (Effects with a duration of concentration, instantaneous, or permanent are not affected.) For example, a cleric who has used his Planar Touchstone feat to forge a link between himself and Empyrea Mere (a touchstone located on the Seven Mounting Heavens of Celestia) grants these bonuses to any creature he summons from Celestia, such as a hound archon.

Special

If a creature's indicated environment doesn't specify a particular home plane, but rather a group of related planes (such as "any good-aligned plane"), you may choose to summon a creature of that kind that is native to your chosen plane and thus apply the feat's effect normally. However, no component of the alignment of the creature to be summoned may be opposed to any alignment traits of your chosen plane for the feat to work. For instance, the cleric in the example above could apply the feat's effect to a summoned celestial black bear (lawful good) or a celestial bison (neutral good), since celestial creatures have an environment of "any good-aligned plane." He couldn't apply it to a summoned celestial lion (chaotic good), since the lion's alignment has at least one component (chaotic) that is opposed to the alignment traits of the Seven Mounting Heavens of Celestia (lawful).