When this set was first released, I did the unusual thing (for me) of buying it at full retail from a Games Workshop store! They are such nice models; probably the best "robot" type figures that GW has ever released.
I started playing 40k many, many years ago, and still have (semi?) fond memories of playing Rogue Trader (with its clunky rules and wayward army lists). The Adeptus Mechanicus robots had rules back then, but they were quite difficult to interpret and had limited models. Even so, like the Imperial Beastmen I still have great memories of those army lists... When the Kastelan set was first released, I just had to get a box and paint them up.
Many months later, here are the results.
The models are easy to assemble, and stand a decent size (similar to a dreadnought). There are fewer options in a box than some similar sized 40k models, and the arms and legs are effectively menopause, but they are just great figures. I love the aesthetic of a the classic robot...
I added weathering to the back plates with MIG weathering powders. The large open armour plates also invite lots of scratches, decal work etc. I decided to keep the weathering artist - using filled-in scrapes and scratches - rather than go over the top with battle-damage. I was tempted to do bright Runefang weathering around plate edges, but decided against that in the end.
Bases were done with Martian Ironearth. This is a strange paint... On drying, it produces a nice crackling/cracked earth effect. Great, I thought, I can base an army with it. But the paint almost immediately becomes flakey. I dry brushed with Kindleflame to add some depth, but after a couple of passes large clumps had fallen off.
In the end, I decided that simple Martian earth bases were also too monotone. What with the red armour, that's an awful lot of red on the same model. So I added some grass clumps (not strictly Martian, but hey; maybe they are fighting in a terraformed sector or something) and a piece of slate to each. These elements helped break up the base colours nicely.