Rift Rippers are powerful weapons that can allow the user to go in-between dimensions. A Grim Aider's sythe is normally a rift ripper.
Rift rippers must be left in a mana-rich environment from sunset to sunrise, and then tempered under the noon sun. This process is generally repeated 3 times to make it mana-rich and strong, then its generally used to kill a living creatue with red blood, absorb its life force, then bury it with the creature. The blade is dug up after two days, and by then, it should work. Alternatively, they are blessed by a higher power.
Rift Rippers can take any shape or form. Goldas' rift ripper had two blades before being reformed into The Godkiller, a different Rift Ripper. Nick Myme's Sythe is a Rift Ripper. Marcus has a blade which is also a Rift Ripper.