Far to the west, in the mountains beyond the Vale of Augury, lie the remains of an ancient power, a fount of eldritch energy nestled deep in the high woods. It is said that the things that grow here, grow strangely. To the forces of nature this is a sacred place, made to stay hidden and unknown. Many are the traps and dangers of this land--all-consuming grasses and crossbred fauna and poisonous flowers--but none are so fierce as the mighty Treant Protectors. These ageless, titanic beings, charged with keeping the peace in this dangerous land, ensure that none within encroach without reason, and none without poach their secrets. For time untold they tended to their holy ground, uninterrupted, only dimly aware of the changing world beyond. Yet inevitably the wider world grew aware of this untamed land, and with each passing winter the outsiders grew bolder. Soon they arrived with tools to cut and with flames to burn, and often the Treants would ponder: who are these fragile, industrious creatures? What now had become of the wild, green world? There came and went an age of questions and of doubts, a thousand summers of long traditions set to scrutiny, while more and more the outsiders died and fed their earth. When all that bloomed had finally finished their say, curiosity had overcome caution. It was decided: a lone Protector would be sent into the wider world, and instructed to wander until the glaciers arose once more, to observe the changing land and its creatures, and to discover what unknown dangers could threaten their sacred ground.
Rooftrellen the Treant Protector is a melee Strength Hero who excels in supporting and strengthening his allies with his beneficial set of spells using the power of nature. He is a natural Tank, offensively and defensively, having both the highest natural attack damage, and the second highest overall Strength in the game. Manipulating the power of the plants at his will, he can grant invisibility and stealth to himself and his allies with Nature's Guise , replenish their health with Leech Seed which also slows and damage his prey. His Living Armor bless his allies with natural protection, giving them bonus health regeneration and damage block. His scariest feature is Overgrowth, though it doesn't deal damage, Rooftrellen summons vines, braches and roots to entangle his enemies, making them helpless and unable to attack for a long time.
Treant is a great support/tank hero, able to heal heroes/towers all around the map, heal himself and his lane partner in the early game to stay in lane longer, while being able to protect himself or his lane partner in the event of a gank by turning them invisible as long as they stay near the trees. His ultimate is considered on par with Tide's ultimate, however it has much shorter range, almost half the aoe, while at the same time has a much longer duration and goes through BKB. Remember, Treant is a tank/support hero. You should not be taking lane farm from a carry, should they be your lane partner, instead focusing on denying and keeping them alive with Living Armor and Leech Seed. However, if you lane with another support, such as Crystal Maiden or Dazzle, last hit as much as you can to quickly reach your core items.
Treant is an early game support and a late game tank. His abilities, aside from his ultimate, are really effective early game, as living armor can keep a tower healed up and leech seed can heal a significant amount of damage. But later on, when peoples max health gets up to about 1500 or so, 300 health from Leech Seed isn't all that much. And late game when a tower gets rushed, its not often that the team can defend it quick enough to save it, thus Living Armor becomes less reliable. Don't get me wrong, it is still a very useful ability, and you should ALWAYS have that ability on cooldown. Always be healing the towers. With such a high strength gain, Treant really beefs up late game with max health, and becomes much tankier.
A side note on his ultimate: His ultimate is greater than Tidehunters in the aspect that Treant's goes through BKB heroes. If you know that the other team has a few BKBs, try to save your ult until they start using them. Otherwise they will use BKB during the ult and just break free. Normally, just try to position your ult to hit as much of the enemy as possible. I personally don't like initiating with Treant's ult, unless other, more useful abilities are waiting for a good time, such as Black Hole or Freezing Field. If Treant initiates with his ult, those 3 seconds are wasted as your team then runs out to attack, instead of starting the team fight, then popping Treant's ult to disable everyone while your team wastes no time to continue the offense.
To start off, you'll want to purchase a Stout Shield, an Iron Branch, a Soul Ring Recipe, and the Courier, being a support. The Stout Shield will allow you to tank some damage while either last hitting or denying for your lane partner and you can keep your health and that of your lane partner up by using the Soul Ring and casting Leech Seed whenever the enemy gets close to last hit. At best, this will force them out of the lane, giving you or your lane partner free farm, and at worst they'll still last hit but you will get healed for 300 health.
Finish the Soul Ring in lane and start spamming Leech Seed to keep your ally's health up and the enemy away from the farm! Then you'll rush Vangard to give Treant a good tanking bonus, with greater health and damage block to stack with Living Armor. Now you should finish a Headdress before the tower fighting begins. This will help your team regen a little health between fights.
At this point, someone should have taken a tower or two, and your team has begun to hop between lanes to push the rest. You should quickly finish a Mekansm to give a good heal and armor bonus during a team fight. Now your team should be easily handling team fights, what with the Mekansm heal and armor and your dangerous 3 second AOE disable with your ult, OVERGROWTH. You can then build a pair of Arcane Boots and sell your Soul Ring. Remember to refresh your ally's mana and not just your own! You should also pick up a Perseverance ring, to build either a Bloodstone or Refresher Orb, depending on what your team needs.
If your team needs more tanking, finish the Bloodstone first, giving a huge health boost, as well as immense mana regen to keep all your spells on cooldown, such as Leech Seed or Living Armor. You can disassemble the Arcane Boots for the mana booster and build Treads out of the Boots. Once you finish the Bloodstone, you can sell the Soul Ring to give you more inventory space. If your ult isn't securing kills well enough or giving a big enough advantage during team fights, rush a Refresher Orb to give a total of 6/7.5/9 seconds of AOE disable. This is a ridiculous amount of time for a complete enemy team disable, and if you manage to finish the Refresher Orb, consider the game over for the enemy team.
If the game has not ended yet, pick from some of the situational items, such as Heart, Assault Cuirass, Radiance, or Pipe, for ultra tanking/support. Radiance is especially helpful as it gives a large damage boost and an easy harassing method while invisible under Nature's Guise.