In Divine Divinity the stats of the items are random.
If you want a good sword with the frost skill, try to get one of the following swords.
First make a savegame, have a look at the stats of the sword.
If the sword does not have the frost skill then reload and try again.
The better swords are these ones :
The [nocando]Sword : Near Stormfist Castle (dropped by a rude knight)
Blade of Chaos 2 handed sword : In a cave at the west of Glenborus, the dwarven village
Brightblade : Near Aleroth (dropped by Lord Seth if you kill him)
Cutlass of Totu Chabahl : Thieves’ Guild (in a locked chest)
Nobleman’s Sword 1 handed sword : In the Holy Weapons Crypt
Random Claymore 2 handed sword : In a lich cave near Rivertown
Singing Blade 1 handed sword : In the Rivertown Sewers (dropped by Pedro)
Sword from the Stone 2 handed sword : In the Stone (Dark Forest)
Sword of the Gods 1 handed sword : In the Wastelands (in a house in the dead village)
Barta