BT6 Double Diamond does not give face to green color, it doesn't even have an SR card, no new LV7 digimon. Bandai introduced new 10 green digimon while other colors have at least 12 new digimon, this is maybe their strategy to boost up popularity for red blue and black.
By the way, Nidhoggmon is still remaining as a very formidable digimon for green color, the power of "returning all opponent's rested digimon and digimon with 5000 DP or lower to bottom of its owner deck" can deal with any type of deck. Last time we talked about how perfect the combination of Nidhoggmon and HerculesKabuterimon, now Nidhoggmon has a "even better" partner in BT6 booster set, it is AncientTroymon
AncientTroymon is quite expensive to evolve (5 costs), same play cost, evolve cost and DP with Nidhoggmon. AncientTroy effect is quite new for green and suitable to put in Nidhoggmon deck. In opponent's turn: When an opponent's digimon attacks, suspend up to 2 of their digimon without "blocker". If this digimon in the battle, even opponent wants to destroy this digimon, at the time opponent declares attacking, 2 of their digimon will be rested by this effect. Nighoggmon deck is normally good to deal with type of deck that can widen the board fast with many rookie digimon.
Once opponent's digimon are rested by AncientTroymon effect, Nidhoggmon can be used in next turn to send all the rested and rookie digimon to bottom of its owner deck. Even if opponent decided not to attack because they scare of Niddhog, then at least AncientTroy helps to delay the attacking.
There is 2 new [hybrid] type digimon in BT6, Arbormon and Petaldramon. Petaldramon is a good candidate to be played from AncientTroy [On Deletion] effect, while Arbormon is used to evolve from a green tamer with only 2 costs. The LV4 hybrid Arbomon is like a game changer for green these days when this digimon can become a last check to win the game as long as there is enough memory.
Evolve from LV5 to LV6 with "0" cost
There is 3 popular Green LV6 digimon is take 5 costs to evolve: Green Imperialdramon, Nidhoggmon, AncientTroy. Using the green Izzy and Mimi or LV5 Jagamon is a step to evolve to LV6 digimon for free. It is easy to hit LV6 card if we have more "Izzy Izumi & Mimi" in the battle.