With the success of the SU-152, being one of the few self propelled guns capable of killing the heaviest German tanks, the ISU-152 was essentially the same thing but built on the IS-2 chassis. The SU was based on the KV chassis which was being phased out of service. ISU-152 was a little taller and had more frontal armor but had similar performance in battle. The biggest draw back of the type was the low ammo storage (only 21 rounds) but despite that it was an important vehicle and still used long after the end of the war.
This is the tier VII Russian TD. It has decent frontal armor but has more punch than most tier VIII tanks. Don't get too far forward where you can be surrounded or flanked though the ISU-152 is much more nimble than other nations fixed gun TD's. It should still keep back and support snipe.