Class Level Summary: Bard (20), Red Dragon Disciple (10), Purple Dragon Knight (4), Fighter (2)
Race: Human
Alignment: Neutral Good
Starting abilities: Str (18), Dex (8), Con (10), Wis (8), Int (14), Cha (14)

Ending abilities: Str (42), Dex (8), Con (12), Wis (8), Int (16), Cha (16)

A must haves are:

1. Mage Armor, Expeditios Retreat, Identify, Protection from Alignment
2. Cat's Grace, Bull's Strength, Eagle's Splendor, See Invisibility, Ultravision
3. Displacement, Dispel Magic, Wounding Whispers
4. Improved Invisibility, War Cry
5. Ethereal Visage, Greater Heroism
6. Energy Buffer

Use Ghostly Visage at early levels, it is strongest buff for first 10 levels. After that it is useless so exchange it. Select Haste spell until you get haste item.

Note that Displacement, which is strongest buff in game currently, can be cast in armor without arcane spell failure since it doesn't have somatic component. I did not take any ranks into Concentration though, so buffing during combat will be hard if not impossible. I am however of an opinion that there is no need to rebuff during combat. Except Displacement and War Cry all buffs are long-term so you just strip yourself naked whenever you rest, buff them and you should still have them when you reach the final boss. If you really need displacement and you really need to cast it during combat, then just run away for a bit and cast it. Unless you are being shot at it should work. Alternatively replace discipline for concentration ranks. Since the build has high AC, discipline might be needless as most monsters won't try even try knockdown.

I selected War Cry as a must have, however nobody ever really relied on this spell in past. The build has enough AB without it. Unlike Displacement it cannot be cast armored without failure. I don't think that this spell is something that you must rebuff periodically. Cast it for bosses and key NPCs, sure, since you have it, but pointless to keep it buffed for entire run.

Should be able to handle all melee dungeons: (HC) Sewers, Labyrinth, (HC) Moria, (HC) Frosty Tower, Den of Evil, (HC) Bushmen.

This bard build is made to be able to play solo, but as any bard it can help in party runs with his Bard Song and Curse Song abilities. With PDK you can also buff allies with additional +2AC, +2 AB, +1 damage and 20% movement speed which is nice.

I think it has really nice base AC, AB and devast DC, high skill ranks further improved by song so you shouldn't need to swap gear in runs like HC Moria. And with Curse Song you virtually get additional +2 AC, +5 AB and +2 devast DC on top of it.