I have been reading through Rites of Battle concerning Dreadnoughts and the sarcophagus. It says that once the sarcophagus has been placed into a Dreadnoughts that it is linked to that one machine forevermore and the Tech-Marines simply replaced the weapons loadouts and power down the walkers between battles.

Whilst I am sure I have read elsewhere that they keep the sarcophagus seperately in stasis and place them back into their machines of war when required and the Battle-Brothers can talk to the Old One between times in their sarcophagus by linking it to a specialised vox unit.

Does anyone know which is the case?

Both could easily be true. In cases like this I prefer to think that some Chapters use one method while other Chapters use the other [or others if that comes up.]

Pretty sure Bjorn was generally depicted as being all walker-ed all the time, even when he was asleep. But the sarcophagus was removable, that has always been part of the background. Don't get hung up on that though, a space marine's power armour is also removable, but you don't see them switching their armour all the time. Its probably a cultural thing. A dreadnought's body is his body until he dies, or it is destroyed and his sarcophagus gets installed in another body.

The fate of dreadnought between mission depends really from witch chapter they came, the time between mission considering how much investment awakning the machine demand, and in witch state is the SM inside the sarcophagus.

For example an Iron Priest of the Iron Hands willingly put in sarcophagus without being a crippled hero would stray awake as long as he wish it. Some of them are "chapter" master.

In contrario a nearly dead SM hero with a body full of pain and quite mad from the wound torturing him and not redally there anymore will be put in stase between mission for their own sake.

Or in the case of Bjorn to have 10.000 years make you quite old and to maintain his sanity facing a world so changed he is put in stasis.

I can tell you what I did in my current campaign. There are three interred venerable brothers in the vaults of Watch Fortress Xerxes, guarded by a Brother-Keeper and many automated defenses. All are in caskets, wired into support systems. One casket is relatively easy to spot, belonging to the one confirmed brother in the vault, a Subjugator. The other two are hidden away, their very existence restricted information for morale reasons. One is a White Scar who was hideously burned by a Chaos Sorcerors' hellfire. He is kept in stasis and when awoken to speak with other marines has to be given such a massive dose of sedatives that it will kill him quickly unless detoxed. This dose of sedatives merely reduces the pain enough for him to speak without roaring in agony. In a dreadnought, he can receive orders and information but will not reply, preferring to close with heretics and smash them to pieces in fury. The last marine is a Raptor who is deep in morbid thoughts. He is obsessed with his own inevitable demise and despises rapid fire weapons, preferring his "last few shots" to be perfect sniper kills with lascannon and missles.

I think the mention of dreadnoughts being bound to their host-casket just means that once assigned, that chassis is kept purely for that battle brother. Between missions and out of combat, i think it depends on how long passes. A dreadnought is not really a general issue thing for a mission, so realistically it would only be deployed for really important missions. However as this is a game and it is possible to be a player dreadnought character, i'd suggest that even if left within the chassis, the casket will be put into some kind of hybernation mode to maintain the sanity and physical condition of the marine interred inside.

From what I understand a dreadnaught will stay awake for the duration of the crisis it was awoken for, wheather that is one mission or several, and then go back to sleep until it is needed again.

Cryhavok said:

I believe this is true. This is why Chaos Dreadnoughts go crazy and become violent; they are always awake and forever removed from the world.

Once more you forget the Iron Hands Dreadnoughts… Some of them are awake all time and lead entire clan… But it is true that those dreadnoughts are freely, willlingly put in the coffer and aren't deadly wounded before being put in the sarcophagus.

Thebigjul said:

I didn't forget them, I simply consider them an exception. Most chapters break one "codex" rule or another. They probably aren't even the only ones that do it.