What is the epic song of a group?

Drat! Can't get this to save as a list.

I'm disappointed to see members mentioning not necessarily the most epic songs by a band, but rather the old, most popular hits that everyone knows by heart.
I must agree with OP concerning Deep Purple and Child in Time. I think that would be their high water mark. Let's see, what else...

Sway - Rolling Stones
November Spawned a Monster - Morrissey 
Accidentally Like a Martyr - Warren Zevon
Precious - The Pretenders
I've Returned - Squeeze
Junkhead - Alice In Chains
Street Life - Roxy Music
It's Over - Level 42
Untogether - Lush
Adam and Eve - October Project

I could think of a million more, but these are the first to come to mind. 

roxy, I admit to being one who didn't take the term "epic" literally enough. I named titles which I consider epically great, but that wasn't the question. Some of mine do fit the term, such as Richard Thompson's "Shoot Out The Lights" and Television's "Marquee Moon". Here's another: Dave Edmund's reworking of Khachaturian's "Sabre Dance" when he was in the group Love Sculpture.

In A Gadda Da Vida / Iron Butterfly
Monster / Steppenwolf

 Hendrix   " Voodoo Child (Slight Return)"
(Originally titled "Voodoo Chile (Slight Return)" on UK Track release)