Below are sample teams that have successfully conquered this dungeon. You are welcome to share your own teams and tips here. (Please reference Sample Team Guidelines for suggestions on contributing.)
If you want to be more non-IAP, use as leader and find another Wood-type. If you have you can swap for to have an easier time. Echidna is for emergencies, ideally max-skill but you can pass even without skilling her up, just be careful. Swept 6F with a nuke from Lucifer, but since I was forced to use Echidna on 5F, you can charge her up on 6F before nuking. 7F after grinding to about 40% use double Gravity+Lucifer to finish.
First part is easy with double Light resist. Charge Lavaulin on 1F, afterwards if you feel like there's too many Low Ninjas then give em a nuke. Leave Mid Ninjas for charging skills. Minerva has Fire resist, so 4F isn't hard either. On 6F when the enemy uses Ninja's Training Secret give him a Gravity and hit him as hard as possible, if you can't then use to take a hit. 7F just make good combos at first, when close to 20% first use and , then push him to 20% with Gravity and dragon nuke. Heal carefully after everyone gets bound, then you can easily claim your egg.
Grind team. My 20K HP could pass the stage lying down, even if you just have 16091+ you can take 2 hits from Hideyoshi with 0 Hearts, but be careful of Goblin - 18445+ is super safe. can change for or , needs other high RCV teammates and be careful of Hearts, should be careful to not hit the boss to 20% too quickly because getting bound means you'll probably need to Stone, and will only increase your speed (Personally I think if you use then don't use Gravity or you might go too fast). Max-skill is for emergencies, though the boss's 2-round cooldown put her on the bench because using is just too cool. Sweep with Lucifer, use Gravity/Lucifer once you grind the boss to 40%. Really the team's key points seem to be just and D:
Just finished beating Goemon with this team, had nothing better to do so came over to fight the dragon and discovered it was doable XD. Siren max skill w/ 3 Hearts healing 4000, levels 52, max, 31+2, 48+10, 32+6, max. Charge skills on Low Ninjas, first kill Hamahime who will bind Light types, nuke 6F, nuke the boss's last bit of HP, very simple. You can kill Low Ninjas directly with Archdemon counters or put a Whiskey Dragon on your team.
16x team, no problem if your HP's above 16090. Passed 5F with Rainbow Keeper due to 5 Low Ninjas + not enough orb colors. 6F beat him below 30% in 2/3 rounds, he'll buff his ATK, giving you 2 more rounds to beat him. 7F will take off maximum 16090 HP, no problem if you can heal enough in 2 rounds.
Double Lucifer team, aside from leader being max, other subs don't have high levels. Hera-Is 40, Kagutsuchi 27, Dark Ceres 20, Light/Dark Venus 85. First 5 floors are easy, if you encounter a high-HP machine gun you can use Change the World. Use one Lucifer on the miniboss, heal up with Ceres at the boss, then charge up Lucifer again to finish the fight with one Gravity + 2 Lucifers. Because RCV is very high, everything is easy if you don't get both leaders bound
Seiryuu/Horus team. Friend max level +65, average lv 40, not max skill and is the key for my team passing this dungeon. is just for boosting HP and can change for other Dark types. is to prevent being orb-starved, skill is 2 away from max. is for emergencies, better if swapped for . Leave Mid-Ninjas to charge skills, Fuuma can be swept with 2 (or 1 plus cascades) 14x attacks. Use immediately against the boss, use orb changers if you lack colors, safely clear and claim your gold egg
All max level aside from Ra, Siegfried +44 all others around +5, Horus is for clearing Low Ninjas with 4x. RCV was a bit on the low side, took around 6 Heart Orbs to heal from Fuuma and Hideyoshi's attacks. First few levels all easy, just activate 4x and you'll basically kill everything, charge skills on Mid Ninjas. I had to activate 24x 2-3 times to kill him, you can still survive Unification if you make an effort to combo Hearts and heal up.
Counts as non-IAP I guess. Average levels around 40, since I didn't raise other Light resist monsters... I had to use the Poring as leader, Wood-type sub can swap for another high-HP defensive monster. The only tough part is 4F, first kill Kodama in the middle, then use poison on the other two guys and grind away. Use a couple of defensive skills if you need it, then finish them off with dragon breath when they're almost dead. 6F wipe Fuuma with a Lucifer nuke, 7F not hard at all use Echidna/Guard/Poison and grind him to 30% then finish with a Lucifer strike.