The Banehammer is a super-heavy vehicle used by the Imperium, a close cousin to the venerable Shadowsword and Baneblade.
It is unknown when the Banehammer was first created but it has had much use, especially during the recent Tyrannic Wars. The vehicle is primarily used by Imperial Guard commanders to halt massed enemy advances.
The Banehammer replaces the Baneblade’s Battle Cannon with a Tremor Cannon, which launches projectiles which bury themselves and detonate only after traveling some distance. On detonation, the shell releases a huge shock wave, liquefying the nearby ground and forcing enemy infantry and vehicles to literally crawl their way through or risk the consequences.
I initially confused this Banehammer with the Doomhammer. The Doomhammer is a similar Super Heavy Tank which was created from the necessity for Titan-killing vehicles during the thousand-year-long siege of Ordana. During the siege, many commanders requested Shadowswords to combat the large number of heavy armour in the form of Titans and tanks from a renegade forge world. The only way the Imperium could maintain the war effort was to retrofit their Banehammers with magma cannons.