• Had picked up the the 'Master Key' at character creation to gain access to Havel and a shortcut to the Halberd wielding Black Knight.
• Killed Havel first for the ring and damn it was hard. This fight was easier previously, because I had encountered Havel late in my first playthrough and had 'Astora's Straight Sword' in my second one. 'Astora's Straight Sword' does a considerable amount of damage with backstabs to Havel, but required investing in faith (which inflated my soul level for that playthrough).
But this time I had weak weapons, tried to backstab Havel with every weapon..they are resulted in weak damage, finally purchased a 'dagger' from the undead merchant and killed Havel a bit faster (39 damage with a dagger backstab)
• With Havel's Ring and the shortcut route to Darkroot Garden gardens open, I progressed straight to the bonfire near the Halberd wielding Black Knight. Activated the bonfire, quit the game to the menu, made backup of my save (just in case the weapon doesn't drop) and loaded up the character. Luck or coincidence; Glitch, Estoc and then the Black Knight Halberd weapon drop, without reverting back to my save files backup.
Glitched past the the Black Knight as I ran/rolled/collided past him, 'Estoc' which I had found in New Londo Ruins helped greatly in the fight against the Black Knight. Fight ended in the open area above the bonfire, by two handing the weapon and using the strong attack which hits from a range.
• With the spoils of progression; Black Knight Halberd, Souls, some Twinkling Titanites, returned to Undead Burn to level up.
Exhausted all souls (and items which gives souls) to level up towards the figure I had calculated; soul level 18 (from soul level 4 of the 'Warrior Class'). Farmed three to four bonfire respawns of the weak undead and killed the lone Black Knight (unfortunately he didn't drop the Black Knight Sword).
Finally once I reached 22 STR and 18 DEX and was capable to utilize the Black Knight Halberd in two hands. Gotta admit the base damage of the Black Knight Harberd is insane for an unupgraded weapon, could kill the skeletons (in the graveyard next to firelink shrine) in one hit and the giant skeletons in two hits. Three bonfire respawns later, gained Murakumo from the first giant skeleton.
-> Objective achieved in around an hour and some minutes: Black Knight Halberd, Murakumo and capability to wield them both. Then decided to progress further. <-
• Taurus Demon...Taurus Demon died in one hit from the falling attack with an unupgraded Black Knight Halberd..one hit. (I never knew this)
Returned to the Undead Burg bonfire, put a summon sign..got summoned into a game where the character was a 'Deprived Class' at soul level 15. Havel died amazingly quick against the Black Knight Halberd, Tauras Demon required me and the host to do a single fall attack to killed it (since I was summoned, I guess the HP for Tauras Demon increased a bit).
Opening up the shortcut from between the dragon bridge and the bonfire in Undead Burg, thought I should upgrade the Black Knight Halberd and went to Undead Parish via Havels tower and through the Dark Root garden. Had enough Twinkling Titanites to upgrade Black Knight Halberd to +3 and enough souls to upgrade Murakumo to +5.
• Proceeded towards the Dragon Bridge from the Undead Parish side. The iron boar died in a single swing from back with Black Knight Halberd (I was surprised), Black Knight wielding the Giant Sword died in two swings too (was even more surprised).
Luck or coincidence; the Black Knight dropped the Black Knight Greatsword, I could wield the weapon in two hands and use it. (hadn't planned for this, but was able to utilize the weapon with the stats I had..in two hands)
Utilized bonfire at the Undead Parish to test the new weapon, the Black Knight Greatswords two handed strong attack does a unique move which literally bats enemies like baseball (amazing, I never tried it before)
...called it a day at this point