5 very long campaign missions, similar to the last few missions in the main campaign. Fully voiced unlike the skirmish campaigns, involving the dwarf queen, additional environmental enemies in scorpions that felt like non-fire lava lumps (but with graded nest difficulty levels so it doesn't feel like the nigh-invincible lava lump nests), additional traps that are fairly fun and damaging enough to be worth including, yet with their own limitations that doesn't make the original traps irrelevant. New hero enemies with new mechanics but I generally tune those out. This is very well done, no skimping on effort whatsoever.
If you're looking for a continuation of the main campaign with more dwarf queen shenanigans, go for this. The additional mechanics doesn't really justify buying this dlc unless you really like D4 (which I do), so if you haven't completed the main campaign and are not looking for more orthogonal campaign missions I would say skip this. Otherwise, it's awesome and totally worth the price, it should be at least 10 hours of additional playtime just to finish the campaign.