The Heroes of the Storm Garden of Terror map has a knack for transformation. It goes through a day and night cycle, and is a pretty straightforward three-lane map when the sun is out. Players battle each other to control lanes and acquire mercenaries to fight on their behalf. But things become more interesting once it sets at the 1:30 mark. At that time, Heroes have two minutes to take advantage of the night.
They must leave the lanes and head into the garden area near the center of the map to hunt Shamblers, which are essentially plant zombies. Once defeated, Shamblers will drop seeds (5 each) for Heroes to collect. Meaning Heroes can acquire 15 seeds from each small group of three Shamblers, while powerful Golems provide 60 seeds each. The first team to pick up 100 seeds will spawn a giant Garden Terror by their core. A Hero has one minute to return the base to take control of the Terror, otherwise it will die.
Once a hero has control of one of these monstrosities, they gain an all-new set of powers and a significantly boosted health pool. Power include Spore Queen's Curse, which transforms opposing heroes into small plants that can't fight back. Overgrowth disables the opposing team's defenses and damages their minions. Lastly, Sprint lets the Terror quickly traverse across the map.
It's up to the team to figure out how to best utilize the terror, whether it be to gain more experience against opposing heroes, break deeper into a single lane, or spread the damage out so that the opposition has a harder time defending.
Do Some Quick Math: There is a total of 180 seeds that are up for grabs each night - 90 on the top and bottom, comprised of a Golem and two Shambler camps. Figuring out what order to take them out is paramount to victory. Typically, Heroes will go straight for the closest monster camp or start with the smaller ones as soon as the sun sets. But, if your team can coordinate an early strike against both Golems, preferably both at once, then you have the potential to earn 120 seeds right off the bat, while opponents are stuck with 60.
The other team has probably done the same math, so your team will either need to figure out ways to quickly take down the Golems, or find fast ways to take down at least 3 Shambler camps and one Golem.
Playing the Opportunist: Keep an eye on your opponents as they fight with the Golems. If one looks severely weakened, then use that opportunity to take them out. Or dive in and take out the opposing Heroes right before a Golem is defeated. Extra skilled players might be able to swoop in and steal seeds as they erupt from a fallen Golem. It's a risky move, but you don't drop any seeds if you're defeated, so it could be worthwhile one.
Have a Terror Plan: Heroes will only have control of a Garden Terror for 1 minute and 30 seconds, so make the most of that time. Keep in mind how even though the Terror deals significant single target damage, and has the ability to disable guard towers, it does not do extra damage against structures. So, it's generally a good idea to have one or two Heroes supporting the Terror. They can deal extra damage when using Overgrowth to march deeper into enemy territory, or set up traps so that opposing Heroes can't get away when the Terror uses Spore Queen's Curse to transform them.
Mercenaries: Garden of Terror is a numbers game in more ways than one. It's always good to have a little backup along when taking a lane during the daytime. Mercenaries are also very useful at night, especially when you find yourself on the defensive against the Terror. However, mercenary camps will vanish once the Garden Terror appears, unless it is being contested. So, time your battles if you intend to use them.
Delaying Tactics: If your team fails to acquire 100 seeds needed to spawn the Terror, then the next best strategy to try to prevent the opposing team from making use of it. If the whole opposing team is on the battlefield, then use every slow and hold skill or item you have to keep the enemy team from returning to their core. Be careful not to kill them outright, since they'll be back in their base, right where they want to be, upon respawn. Trying to delay a whole team of Heroes for a full minute is a daunting task, but very satisfying if you can manage to pull it off.