One of my favorite Dragonmech weapons is the chattersword. It's very similar to the Chainsword of Warhammer 40K fame, but bigger for two hands.
So herer's my updated version of the Chattersword and a power!
Proficiency Bonus +2
Properties: High Crit, Chatter
Group: Heavy blade
Chatter property: Weapons with the chatter property deal 1 + enhancement modifier of the weapon in ongoing damage(save ends) or increases ongoing untyped damage by 1, against a target hit by the weapon if the attack also would have hit the targets fortitude defense.
Steamborg At-will 1
The teeth of you your weapon digs into your enemy ripping flesh and sinew from bone.
Requirment: You must be wielding a weapon with the Chatter property.
Con vs AC
Hit: 1[W] + Con modifier damage and 2 ongoing damage(save ends)
Level 11:1[W] + Con modifier damage and 4 ongoing damage(save ends)
Level 21: 2[w] + Con modifier damage and 6 ongoing damage(save ends)
The damage probably needs some work but it's a start.