Rockstar Consortium, a patent-holding company formed from the bankrupt Canadian telecom company Nortel, sued Google and manufacturers of Android phones over patents almost two months ago.

Since Rockstar is part owned by Apple and Microsoft, the move looks like a major escalation of the patent wars that have brewed over Android.

This week, Google filed its counter-attack seeking to invalidate Rockstar's patents. That's a normal step for a defendant in a patent suit. But notably, Google didn't file in the East Texas court in which it was sued. Instead, in a play for venue, Google has sued Rockstar on its home turf in Northern California.

Among other reasons the dispute should be heard in California, Google lawyers note that Apple is a large shareholder and has a seat on Rockstar's board of directors. Google also says that Rockstar started farming out its patents shortly after its formation and transferred more than 1,000 patents to Apple alone.

The new lawsuit (PDF) also notes that Rockstar has reached out to hundreds of other companies in recent months seeking to license the patents. Much of that activity has gone on in California. "In fact, Rockstar’s CEO has stated that it would be difficult to imagine that any tech companies—legions of which call California home—do not infringe Rockstar’s patents," write Google lawyers.

Rockstar claims that its business is a suite in Plano, Texas, "but the substantial majority of its employees, including senior management, are based in Ontario, Canada," notes Google. "Rockstar Consortium is admittedly a 'patent licensing business' that produces no products, and instead exists solely to assert its patents... Rockstar intends the Android OEM Actions to harm Google’s Android platform and disrupt Google’s relationships with the Android OEM Defendants."

Rockstar is owned by Apple, BlackBerry, Microsoft, Ericsson, and Sony. The company paid $4.5 billion to acquire the Nortel patent portfolio, the largest sum ever spent on patents.

Google's counter-suit, filed on Monday, was first reported by GigaOm.