I don't know about a warhammer, but a Dwarven Waraxe would be thematic. Another option is to design a weapon using the Weapon Creation rules in Weapon Master Handbook. It could have both a hammer and axe face so it deals Slashing and Bludgeoning damage. A 1-h exotic weapon has 8 base design points and costs 8 gold. An additional damage type costs 1 DP and Traditional(Dwarven) costs 1 DP so you have 6 more DP to work with. You could add 2x crit range for 7 which means you need 1 additional DP which increases the cost by 15g, or just 1x crit range for 3DP, leaving 3 DP for damage increases, taking you to 1d8 damage. If you really wan to splurge, get 3 additional DP (increasing price by 45g) and get both 2x crit range and 2x damage increase which gives you a 1d6, 18-20/x2 crit, B or S exotic weapon that counts as martial for dwarves and costs 53 gold. Or, you know, just go for a Scimitar for the crit range. There's no rule that says that your Blackblade is the only weapon you can use; you could carry that as well as your family warhammer.
