This was inspired by a build from Billyshere which I modified to work a bit smoother on ruthless. 

Black arrows denote where the DSTS should aim.

The relevant stats posted are the main stats I had when I used this build (can probably be cleared with lower, but not tested)

Some notes:

1. On first wave: drop mana to app using your tbooster -> build lightning towers -> purity bomb -> build DSTS. Not purity bombing has made me lose to kobolds sometimes.

2. I do NOT use Ini for this build; the mob counts on ruth are quite low, but the last 20-40 enemies are all slogres which are better dealt with using jester wheel (in my opinion)

3.  The reflects can feel useless since sometimes the snotballs just hit the pillars. The healing aura helps alleviate that  =^)

4. You can replace the darkness traps with an LT but I like them there for the slogres that like to stay out of the strength drain range. Having darkness traps can also help lower the range requirement for aura monk (mine was 9.4k with 4 void) . The gas trap is for thicc djinn.

5. Your ensnare should be large enough to reach goblin copters that come close to north crystal; if in ensnare, they sometimes drop their ogres to their death

6. Last wave is DPS monk, tower booster, and 2 guardian squires/barbs. DPS monk preferably has a ranged pet like an airplane because demon likes to fly.

7. When fighting Annatar, stand in healing aura. As long as healing aura is being boosted by tbooster, you can tank annatar even with C Ninja skin.

8. You get 2 guaranteed ice picks from your guardian boosters, and you have a 1/3 chance to get an ice pick from each monk. 

Good luck farming! I hope you hit your double cap divine ice picks.