so i was dreaming last night, Lucid Dreaming... and if you arent familiar with what that is, its an ability to fully controll and play around with your dreams..
that aside i traveled to the core.. and at the story i develop in my dreams.. i entered the core, i wont be explaining you the whole story coz that would take at least 7 pages.

so while i was there i meet a creature thats possibly behind the echostones and one "traped" inside the core. it was a spiral knight - like creature, well simular to them.. with pure white body, possibly a female (ehh..) the area i was in was sorounded by a cube like white structures... she put her hand on her chest and then put an item in my hand.. before i was sent back to face the swarm. i had the white like cube in my hand... witch soon transformed into different items, guns or swords, like it had a mind of its own, and helped me fend off the swarm..

SO after that little story back there, we go back to my suggestion.

The weapon was called the Heart of Memory (dont ask me how i know)
and here is my idea -

it would be a craftable 5 star "weapon" in Sancuary (possibly avalible with the releace of the 5th boss)

It would resemble a white cube of a sort. it would do high normal dmg. and have Very High dmg vs swarm type monsters
to craft it player will have to Obtain all 5 Echostones and use them to craft the Weapon (you will not lose the artifact, however by the lore they will "fuse" togeder makeing the weapon)

now here is the trick:
weapon will starts off as a white sword, that works in sumular way calibur does. but on charge attack it would create a explosion around the knight, a size of 3 or 4 star bomb... and switch its form into a gun, possibly valiance. it would on next charge attack send out a big bullet, like valiance does that would have a bigger explosion radius.. and turn back to sword.. basic attacks would be same as the weapon its form is takeing.
charge attacks would take slightly longer then usual, simular to gran faust

sense the weapon is... Multi-weapon.... i see 2 solutions for the Bonus Dmg/As/Ctr it Draws from its armors-

One - weapon takeing its power from Multi buff armors like Chaos or Armor of the Fallen and Swiftstrike...
Two - takeing its bonuses from Any kind of Buff (its still normal dmg, so it cant get stronger then Weapons like Piercing, Shadow and Elemental when they are used agenst targets they are strong agenst, and it would make it an exelent backup weapon regardless of what you play)

and another possible problem - where would weapon show in Inventory?

Artifact tab (weapon itself is, as i mentioned is "made" out of 5 echostones, and being a unique that it is wont hurt leaving it as a special Artifact, hell it could also hold more info from... whoever left those artifact in first place, as well as be awesome weapon for combat )

It is Bound to player, just like Proto gear and Expansion Gear

My apology for my terrible spelling
so.. lets Hear your ideas, thoughts, and ofcorse my all time favorite, balancing issues!