The garden is the second to last stop on the way to the final showdown with the Baron.
It's a changing encounter, similar to Karazhan's Opera event. There are four different options for the bossfights, all of which are explained in their respective links, to the right.
The area itself, though, is a hexagonal walled garden area with a latticework covering. The latticed roof is to prevent the raid from seeing down into the garden before the third tower's door is opened (explained here). The basic landscape is unremarkable, with a gentle sloping rise in the center of the area, and a single well off to the right hand side of the raid as they enter the garden's main door.
This well serves as a means to taint the garden. The Baron, in his quest to find a means to harness the powers set loose inside him, has subjugated Cenarion Druids and bent them to the task of trying to harness a cure through their close contact with nature itself. The spirit form of one of these druids reaches out to the raid as they near the garden door, and calls out them through the Emerald Dream.
"Wait, young ones! Beyond this door lies a force bent to the will of the Baron, but it is a force acting against its own will. The creature you will encounter in the garden of the Baron is not an evil entity, but one that is merely lashing out in desperation at everything in its path. Like a cornered beast these Spirits of Nature are simply exhausted and frightened. The garden must be cleansed, but I'm afraid the only way left to do that is to purge the evil that has infected it, and hope we can begin anew.
If you brazenly strike forward into the Garden you will suffer a dire fate, I fear. The Baron has amplified the magics at work here, and they must be put asunder before we can hope to stand a chance.
Within the garden grows many plants and herbs. Collect 10 Death Lotus that grow within, being careful not to engage the Spirit of Nature prematurely. When you have all 10, bring them to the well and hurl them in. I would advise you to be quick about this, and throw them all in at once, as the Spirit won't take kindly to this affront, and will likely try and put a stop to your meddling.
The Death Lotus will weaken the spirit enough for you to stand a fighting chance, I believe. Go now, and cast the Baron's shackles off of our friend inside. It won't be easy, but I believe you can do it. I will see you inside, once your task is completed."
The raid carefully navigates the outer ring of the garden, looting plants that are UNIQUE. One raid member can carry one such herb, and as the druid mentioned, there's kind of a timer involved from when the first one is thrown in the well. Basically, ten people go loot a flower, then come back to the well and wait for the signal. Once the first person goes, everyone has 3 or 5 seconds to throw theirs in as well, and then the boss activates. The '10 herbs' gives a percentage scale that can be tuned for an achievement... only throwing 5 in weakens the boss halfway (5x = 50%)... perhaps there could be an achievement where only 3 herbs are thrown in the well, but the raid is still victorious?
Once the specific boss of the garden is defeated, the Spirit we battle slumps down... exhausted, but otherwise 'cleansed'. We don't actually 'kill' them, so much as 'overpower' them (down to 1%, where they go green), and break the spell the Baron has placed on them. A swirl of leaves coalesces into a vision of Malorne, which kneels by the fallen Spirit. The druid we met outside in spirit form is joined by others who form a ring around the fallen boss, and they channel a spell that swooshes the spirit's fallen body together into a tornado which flies high up into the sky, and then twirls back downward as a shining seed which plants itself into the soil of the garden. The druids complete their ritual, and a sprout appears.
"Malorne is pleased with your help; the garden is cleansed. New life has begun untainted by the reach of the Baron. We of the Circle are in your debt, and wish to grant you these gifts from the gods.
The final barrier to the Baron himself has been removed. Go quickly, ascend this final tower, and rid this land of his evil once and for all!"
The druids and Malorne all fade away, leaving a large Cenarion Satchel on the ground, which serves as the raid's loot chest.
