Venerable Dreadnought 4th Edition - warhammer 40k

Venerable Dreadnoughts are the sarcophagus of heroes of a Chapter's past, entombed into the Mark VI Castaferrum pattern, believed to be inherently susceptible to the corruption of Chaos, and as such are covered in purity seals and daemonic wards. Like all dreadnoughts, they are kept in stasis chambers prolonging their existence when not in battle, and only awoken for key battles or in direst need

The memories of the ancient heroes who pilot them can extend back to the founding of their Chapter and its earliest history. Thus they are revered by other Space Marines, not just as potent warriors of legend, but also as ageless forebears and living embodiments of battles fought long ago. Venerable Dreadnoughts are keepers of tradition and custodians of knowledge, whose advice is sought by battle-brother and Chapter Master alike, lending wisdom to strategy as they do fury to the battlefield.

Having fought in thousands of battles over millenias, they have gained vast knowledge of warfare and are experienced in almost any situation. Having become nearly impervious to harm and and combined with their knowledge of warfare and the galaxy, these Dreadnoughts have become very difficult to destroy. Ultimately, it requires the utter destruction of their sarcophagus to stop them.

Space Marine Chaplains who are entombed in dreadnoughts are known as Chaplain Dreadnoughts.