Yesteday, valve release new mod for dota2 The Siltbreaker, I played a few games and still don't know what to do for my win, and as additional question what is reward for complete this campaign.
The most used team composition to win are, Drow-Jakiro-Abbadon-Witch Doctor. So start with that. There are multiple rewards at get. Each section rates your team out of 3 stars, if you get a star you get a reward; the more stars the better. If you complete the campaign you get an emote and a trophy to prove you've done so.
After weekend of many test, I can say most important thing on way to win is right chose of heroes, good team should have good tank best are LC/Abbadon 2 strong damage dealers, I prefer SF but DROW/TA/LINA. as healer you should pick WD because maledict can be very useful on bosses. In every zone you can get 0-3 stars, 0 means no reward, and after each start you will get better reward, for 3 stars you will get treasure with old treasures contains items/sets. Special drop from this treasure is +5level to yours battlepass and very rare is Baby Roshan-Desert. In game are 2 secrete shops /Very big Invokers/ which can sell you random item for 500golds, if you have a luck you can get more expensive items. If you visit both of secrete shops, vendor /Very big Invoker/ will help you in fight with last boss. In dota2/battlepass/campaing you can see map of zones where you already was and conditions to make it to more stars, reward for stars you will get only once. When you defeat boss you will get emote and throphy. Item builds are very different but most often on last boss are atleast 2+ dagons, which worsk great with Maledict, You need Gurdian Graves on healer/WD/. On a tank LC/Abadon you need have a Radiance, everyone in team should have a HoT. In a special treasure across the map you can find Artifacts, they can be very usefull in yours attempts to reach a final boss but they are not recommend to fight this boss because most of time you can afford better items. You can find tutorials to 3stars in every zone and final boss at DotaCinema youtube chanel