About 3 months ago (maybe a couple weeks more) I started saving up primordial saronite for the turn in to gain Shadow's Edge The rest of the materials, I felt, would probably be available by the time I finished. And I was right. The solo quest item (the hammer) really wasn't that tough to obtain, but our guild is at the point where we're trying to down Festergut and Rotface in ICC 25 right now, and that's exactly where we were when I bought my 25th primordial saronite.
Let me just say, if anyone out there is interested in this quest chain, be aware that it is neither short, nor cheap, nor easily obtainable.
So, for a quick recap, if you want to start this quest chain, the first quest you have to turn in requires you to be friendly with the Ashen Verdict. If you're grinding your way to the 25 Primordial Saronites, don't worry about this, as you'll probably hit exalted long before you get enough frost emblems to buy them all anyway. Once you hit friendly, you're given the quest The Sacred and the Corrupt which requires you to return to the forge with:
1) 25 Primordial Saronite which can be bought by frost emblems (23 each, total: 475 frost emblems), off other people and the Auction house (for about 1800 each total: 45,000), dropped off ICC 25 bosses (at about a 10% chance, possibly more for heroic) or any combination of the above. Obviously the speediest way is the most expensive, and I estimate that you can easily obtain about 49 frost emblems each week if you can do one heroic each day, the raid weekly each week, the first four bosses of ICC 10 and 25, the frost watcher in VoA on 10 and 25, and complete the ICC weekly quest on 10 and 25. Of course, you may not have time for all that, so scale that back accordingly.
2) Light's Vengeance the hammer of Arthas. It's really not that tough to get this item. Several strats are available, but if you're like me, and you have a tank off spec, just use that. Go into the cave, start the guy going by touching the hammer, then make your way to the hammer (where he threw it), use Demo Shout until everyone is in close, then Shockwave, grab the hammer. Now, you have to go try to pick it up again, and you'll have to fight the boss, but he's fairly simple. If you can solo Threat From Above, you'll laugh at how easy this guy is to take down. Quest done.
3) Rotface's Acidic Blood and Festergut's Acidic Blood are the last two things I need. These only drop in 25 man ICC, and only one per boss downed. So, if you're one of 10 warriors/dk's/paladins that want this axe, be prepared to have to wait through them unless you've done the leg work to get everything else up to this point. Note that getting this ready could take up to 30 weeks or so, but if you have a ton of gold, could be done in a day.
Once these are turned in you have Shadow's Edge, a really amazing axe in and of itself. But the best part is, that you then can pick up the quest A Feast of Souls which will take you a few raids to complete (1,000 souls actually goes faster than you'd think, but it's still not 'quick').
Once that quest is turned in, you get three new quests to infuse your axe with Unholy, Blood, and Frost powers and then slay Putricide, Lana'thel, and Sindragosa respectively.
Once these quests are all completed, you will need to obtain 50 Shadowfrost Shards, which have a 25-50% drop rate off each boss in ICC 25, and about a 50-100% drop rate off each boss done in heroic mode in ICC 25. Note that this means on an average raid week period (12 bosses including Arthas) you could see between 3 and 6 drop in normal mode, and between 6 and 12 drop in heroic. At most, then you'd expect to be able to complete this phase in 2-4 months on regular mode, assuming you're the only one in your guild collecting them.
Once this is complete, you'll be given the might of Shadowmourne and Darion will ask one final task of you, take down Arthas.
As you can see, this is a fairly epic questline, but the end result is definitely worthwhile if you have a guild that is intent on clearing ICC 25, and you're interested, good luck to you.