To quote Baron from the other thread, this answers alot, for more you really need to read Collected Visions
+I don't know who Malafax is but the Blood Thirster Sanguinius fought was Ka'Bandha.
+There were 7 Legions present (in entirety or part):
Sons of Horus- Horus' reserve force
Emperor's Children- they quickly tired of the Siege and embarked on a genocidal campaign against civilian populations
World Eaters- at the forefront of every assault
Death Guard- the anvil to the World Eaters hammer
Thousand Sons- conjured daemons and used their sorcerous arts to bombard the loyalists
Iron Warriors- used thier expertise in Siege warfare to bombard the Palace and thie Imperial Fists fortress adjacent to the palace
Word Bearers- (only about 40 companies) similar role to the Sons of Horus I imagine
+The Emperor wasn't present during the fighting, he was on the Golden Throne preventing Terra from being overrun with Daemons from the Imperial Webway
+Blood Angels were the first Legion to arrive at Terra in force with the White Scars and the majority of the Imperial Fists reaching Earth just before the Traitors
+There's not really a record of how many lives were lost but for the majority of the Heresy the loyalists suffered heavier losses than the traitors
+When the Emperor arrived at Horus' throne room Sanguinius was already dead, brutally murdered by Horus (at the same time he died the darkness within the Blood Angels that had been uncovered by the actions of Ka'Bandha was unleashed and the entire Legion went berserk and threw themselves at the traitors outside the walls of the palace). For most of the fight Horus was winning and virtually ripping the Emperor apart (ripping an arm from it's socket, crushing the side of his face etc) until a Terminator/Custodian/Army Trooper etc wandered into the throne room attempted to save the Emperor and was casually flayed by Horus- that was the last straw for the Emperor and he gathered his power and obliterated Horus body and soul.
+Kharne was found a top a mound of his victims outsides the walls of the Palace, for some reason the World Eaters felt compelled to retrieve his body and it was discovered Kharne lived still.
+With the death of Horus it was pretty much a case of every man for himself with most of the traitor army being left behind with only the Traitor Legions and Titans being successfully extracted for the most part.
As for where and who. On Terra the Blood Angeks defended the inner palace and ramparts for the most part. The Imperial Fists were stationed in the lower hab areas or somewher similar, don't have CV on me to check. The White Scars did hit and run attacks in the traitors flanks with imperial armoured divisions. Eventually the Khan decided to attack and retake the Lions Gate spaceport, successfully cutting the flow of traitors coming in by half.
Attacking Terra were the Sons of Horus, World Eaters, Iron Warriors, Emperors Children, Thousand Sons, Death Guard and elements of Word Bearers. The Emperors Children grew bored of the Siege though and instead attacked the civilian populace outside the walls, indulging their hedonistic and twisted desires.
The rest of the Word Bearers were attacking the Ultramarines at Calth. However the Ultramarines won, pushed through and made for Terra.
The Night Lords were engaging the Dark Angels and terrorising other imperial worlds. The Dark Angels also managed to win and fight through to make for Terra.
The Alpha Legion were attacking the Space Wolves, and were doing a good job until the Wolves received help from an 'unexpected corner' who or what these reinforcements were will likely be revealed in the HH series. And then the Wolves also made for Terra.
So now the Dark Angels, Space Wolves and Ultramarines were all converging on Terra only hours away, which caused Horus to take a gamble and lower his shields.
The Iron Hands, Salamanders and Raven Guard were all recovering from Istvaan V