Polaris was released in 2012 by Germany's Hüll breeding institute, and it stands apart from every other German hop on this site for one simple reason: at 18-23% alpha acid, it's easily the highest-alpha hop Germany has ever produced, rivaling the most potent American bittering varieties. That alpha acid alone would make it notable, but Polaris is better known for an intensely strong menthol and mint character, distinctive enough that a heavy addition can genuinely dominate a beer's aroma the way few other hops can.
Because that cooling, menthol-forward character is so assertive, Polaris is generally used sparingly and deliberately rather than as a default bittering hop, even though its alpha acid alone would make it extremely efficient for that role. A small amount goes a long way toward giving a beer a genuinely unusual cooling sensation that most brewers either specifically want or specifically avoid, with little middle ground. At an alpha range this high, even a small weight change moves Polaris's calculated numbers substantially — the IBU calculator makes that swing visible before it's brewed. Magnum is the closer substitute for pure bittering efficiency without any menthol character at all. Northern Brewer offers a much milder mint note if a hint of that quality is wanted without Polaris's intensity. German lager styles occasionally use Polaris in small doses, and some modern craft brewers use it deliberately in menthol-forward specialty beers.