Predecessor Builds > Mourn > I am Groot. Mourn Guide!
After extensively testing Mourn on an alt account I have found this is what works best for me.
Mourn is a solid tank but REALLY needs to damage items to do work. He excels in Offlane, with support being a great second choice and can be flexed into Jungle (though this is definitely his weakest role, it can still be effective if you know how to properly Jungle).
Now for tips and tricks:
Your passive heals you: this is great for brawling, however if your in offlane be careful going against greystone, as his passive blocks your passive and you wont be healed.
Charge your hook: Hold the hook for 1 second to get max range, i've seen too many people complain about it, so HOLD IT!!
Channeling your E is not required: Channeling E only increases its range, if your close enough its not worth channeling, just let it rip.
E into Hook it a strong combo, you should practice this as it can take someone out of the fight long enough to secure a kill.
Guard jungle objectives with your E, enemy jungler cannot smite the buffs if you charm them.
Your Ult: While your Ult is a great way to start a gank, it can also prevent one. If you see someone getting rotated on, using your ult to help them get out is worth it.
Last but not least, dont forget your Q also heals and gives armor to you AND your teammates, it can save their ass and yours!
Now get out there and make people hug some trees.