Hand of Fate

If you are looking to farm this achievement, there is one method I found to be quite effective.

While this can be done in Endless Mode, I would recommend loading the Queen of Skulls story dungeon and progress until you get to the final fight against the Queen herself. This should load you into a map that has a coffin in the middle of the map surrounded by spear traps, the Queen herself, her skull lackeys and finally a skull spawn point.

To make life easier, first take out the Queen and her rifle bearing enemies as these are the enemies that will likely do the most damage to you. Now you should be left with only skull enemies with swords and shields which will infinitely respawn as long as you do not destroy the spawn point.

It's at this point that you can begin farming. All you need to do is try to remain on the opposite side of the coffin in the middle from the enemies and they should try to run towards you through the spears thereby getting themselves killed.

All you need to do is rinse and repeat until you hear the dealer mention something about the traps and the achievement should pop.

Happy Hunting.

If like me, this achievement wasn't unlocking for you when you thought it should this is what I did and it unlocked.

Play 'Endless Mode' until you find a 'Ratman Hunting' card preferably around dungeon level 7-10 (any higher and you'll die too fast and the enemies will live for way too long). Hopefully you'll get 12 or more rats. Then the next thing to hope for is a map that has quite a bit of traps on it. Then I simply ran around trying to dodge the traps and make the rats get hit by them. I would avoid bashing the rats or hurting them in any way, to prevent you from possibly killing them. This allows you to get 10 trap kills all in one match.

The only other things I would suggest is to grab a Heavy armor of some kind, preferably 'Immovable Object' and as many health gains as you can come across.

Also, if you die while trying this, simply dashboard, quit the game, load the game, and try again right where you left off (I didn't have to do this, so not sure if it will stop you from unlocking the achievement. I don't think it would)

I got this achievement in Story Mode: Queen of Skulls encounter there is a large stone coffin surrounded by spear traps. I ran around this luring my foes into running on to the traps and managed to get around 7 kills in this one encounter. Allow the traps to do the killing while you do the luring

Another great level which appears frequently is one where there is a path leading to a bridge, if you go onto the grass there are lots of sort of venus flytrap traps, also there is a trap which fires arrows when you step in its direction. This level is also really good, just bash, lure or knock your foes into these traps.

This is cumulative so every fight with a trap try and get at least one or two and this will pop sooner rather than later