Looking for songs with powerful and poignant endings especially when it has a buildup to them, preferably within the death/black genres. My favorite examples:

Insomnium - In the halls of awaiting @ 7:07
http://www.youtube.com/watch?v=NqEYKnHx ... re=related

Vehemence - She never noticed me @ 5:11
http://www.youtube.com/watch?v=0NNCoif_6FQ

Ikuinen Kaamos - Ascent @ 6:34
http://www.youtube.com/watch?v=zyGTaJBaOZ8

Evoken - Tragedy Eternal @ 7:05
http://www.youtube.com/watch?v=6n0sR4b_xXc

a darker more brutal example: Dead Congregation - Teeth into Red @ 3:30
http://www.youtube.com/watch?v=29U55hcbAzw

Always loved The Reign ov Shemsu-Hor from Behemoth's album Demigod, Very epic closer and very epic. Obvious one though

Enslaved - The Watcher, really powerful and the most immediate song on Vertebrae, very good closer.

The Epigenesis have a very good self titled song, very long and epic, kind of a Melechesh jam, very cool.

Both Hail Of Bullets albums have really epic closers, check them out.

I find the ending of Omnium Gatherum's Everfields to be quite the epic conclusion. http://www.youtube.com/watch?v=10lLxc_PpYI

http://www.youtube.com/watch?v=Ld-q02l5pqE

I've always found the ending to Nokturnal Mortum's "Valkyrie" to be pretty fucking epic. Thunderous drumming under some great tremelo picking. The whole song itself has a wicked atmosphere, one of my personal favorite's from them.

SuidAkra's "The IXth Legion" has a great ending as well with the bagpipes fading off into the distance.

http://www.youtube.com/watch?v=KmyL2EwHu3g

Borknagar's Dawn of the End.

One of the greatest, that almost no one knows about, if the very end of Klage's song "Die Weihe des Eises - Eine Großweise". It's a massive song, over 20 minutes long, but it builds to this orgasm of a finish, with one of the best black metal riffs ever written.

How about !T.O.O.H.! - Kali?

Ayreon's Day Twenty: Confrontation is basically a huge (and terrific) build up for the song's climax.
http://www.youtube.com/watch?v=HYwAfCtdGmU
Beautiful, beautiful piece. Also, Bathory's Twilight of the Gods goes without saying.

Checking all these out. Thanks for the recs

Quoting the top youtube comment on the video:
"This outro reminds me of why I listen to music." !!!

the end of agallochs "to drown", it completely makes the song.

They're definitely not a favorite of mine, but the end of Dimmu Borgir's Gateways is pretty lush and epic.
The song builds up very nicely to it.

Last journey of the Ringhorn-Blut Aus Nord, soo amazing
Black Lake Nidstang-Agalloch
Her ghost haunts these walls-Nocturnal Depression (this one is DSBM, but its absoultely amazing)
Abigail-Happy Days(same as above its DSBM)

and totally not metal but Epitaph-Hey Rosetta! If your indie at all then you'll love it, its absolutely touching
oh and Basket-Dan Mangan while im at it

Hollenthon - Conspirator @5:13

http://www.youtube.com/watch?v=TI2eGSN3ffc

Aeon's God Of War is an excellent closer, both in the album and song sense.

Specifically from about 3:50 onwards.

http://www.youtube.com/watch?v=9pVZyzrLO7c

It helps a lot more if you listen to the entire album before, which is no problem because Path of Fire is completely worth it.

Also suggesting The Black Dahlia Murder's I Will Return, an excellent closer to an okay album:
http://www.youtube.com/watch?v=RS4o37I5dMk

Insomnium has several songs with these kind of endings, so it's more or less like striking a gold vein.

At the Gates of Sleep @ 4:16
Last Statement @ 4:10

Be'lakor:
Countless Skies @ 7:16
Sanguinary @ 6:20

Amorphis - My Kantele @ 3:49 (one of the best key changes ever)

The rest aren't strictly from the death/black genres

Constantine - The Darkest Grace @ 9:49
Amorphis - The Orphan @ 3:18
Iced Earth - A Question of Heaven @ 3:14 (a classic)

Immolation's 'the rapture of ghosts' and Severe Torture's 'grave condition' come to mind.
Insomnium'sclosing solo reminded me of Cradle of Filth's 'forgive me father I have sinned'. Now before you go puke I suggest you listen to that song, I'm no fan of their current work but this song has one of the most epic fucking closing solos I've heard.
If you want an epic close in terms of slow death kind of heaviness, 'unto infinite twilight/majesty of infernal damnation' by Incantation is perfect.

limbonic art - dynasty of death

http://www.youtube.com/watch?v=xrz5niwpqBw

what a freaking epic, 5:56 to 9:34 is just a huge release of energy. pretty heavy riffing for black metal too.

Burzum - Key to the Gate @ 2:58

http://www.youtube.com/watch?v=gWynJCi_DSY&t=2m58s

A true classic in my eyes.

Even tho they're not exactly Death nor Black metal, Gojira's Backbone has that epic ending which either makes me viciously tap my feet or destroy my neck from headbanging, it totally makes the whole song.
When I think of it, Gojira's From Mars to Sirius has more songs than just Backbone with really awesome endings, there's also Ocean Planet, Where Dragons Dwell and Flying Whales.

Yay, I've been quoted!

http://www.youtube.com/watch?v=Egw9BCKjHqk

I also recommend OPETH - BLACKWATER PARK. That song is the definition of build-up to a fantastic climax. It's god damn cinematic. Just perfect.

http://www.youtube.com/watch?v=Cb9C1u8HsR8

digging up an old thread, but i'm quite fond of the ending in orgone's vomited hyacinths, with most of the instruments fading out and the powerful vocals continuing on for a moment; always makes me want to listen to the whole album again
http://www.youtube.com/watch?v=F3_ieGPEd5A

also,

2nd'd

About half of Windir's discography.