In order to create this weapon the forger must sacrifice all of his/her current paladin spell slots, any spell slots gained after the creation of this weapon are gained as if the forger was starting at level 1.

Holy Avenger (modified)
This sword is about halfway between a standard long sword and a great sword in length and about twice as think as a longsword. This sword can split into 2 seperate swords.
While combined: 1d12 magical slashing +3 to hit and damage
While split: each blade is 1d8 magical slashing +1 to hit and damage on each

The sword also has the following properties in addition to the normal ones.
Mountains Strength: While attuned to this sword the wielder has resistence against grapple checks. The wielder cannot be knocked prone unless it is self inflicted. While your feet are touching the ground you cannot be moved against your will.

Chosen of Grumbar: While attuned to this sword the wielder also gains the benifit of the Improved Divine Smite feature, if you already have this feature the bonus is doubled. In addition you gain an aura of 10 feet in which any oath made is bound to the speakers soul, the speaker is compelled to keep its word (if kept heavily regulated). While in underground natural caves and in mountain regions the wielder cannot become lost.

Grind up the 2 obsidian short swords into fine powder, work powder into the metal. Obsidian is not just another stone to a follower of Grumbar, since it is the lowest most base form of stone it is the most stable and unchanging. Even when powdered it retains its properties and is an effective bastion against anything that brings change.