Is there a way to make an animal companion gain the Dark or Shadow template

[SangoProduction]

Or any similar template

[Kelb_Panthera]

Collar of umbral metamophosis on tome of magic page 156 should fit the bill.

[SangoProduction]

Collar of umbral metamophosis on tome of magic page 156 should fit the bill.

Ah true. But that costs money which I can't really obtain lol.

[Forrestfire]

There is also a magical location in Cormyr: The Tearing of the Weave that will net you a better version of the Dark template for a few thousand gold. It requires the buddy system to safely make it through the process though, and turns the user evil. Pretty awful to make an animal companion go through that XD

Those two are the only way to gain the template outside of paying the LA for it, and the only way to get it on an otherwise normal animal companion.

[Inevitability]

There is also a magical location in Cormyr: The Tearing of the Weave that will net you a better version of the Dark template for a few thousand gold. It requires the buddy system to safely make it through the process though, and turns the user evil. Pretty awful to make an animal companion go through that XD

Technically, the only thing that happens is that the alignment shifts one step from the base creature and rarely results in Good creatures. That means that a TN animal companion would have less than a 33% chance to turn Evil, by RAW.

[Taveena]

Probably not helpful, but the Shadow Familiar feat with Theurgic Bond can let you get a familiar with the Dark template that progresses off your effective druid level. Providing you meet the prerequisites.

The Medium and larger familiars from Complete Warrior are a good choice for this.