I would trade in Scyl for WM, because I am guessing your runs are not speedy and all WM bring is Def down, which ninja can do on the boss.

I Would build her all Def and HP to res the people whoi die in the waves.

You say you can't pass stage 18, you are stuck at the waves there. Stage 18 is force affinity. 4 from 5 of your actual team have weak affinity in this stage. Maybe you should change your dragon team for that single stage and use spirit affinity champs instead. You can go back to your actual comp after that, especially stage 20 should be no problem for them.

Or since you probably don't have many 6star champs, probably adding scyl even as weak affinity and not ascend u should be able to manual past 18.  

Like minin stated, just go for sustainability in your team.  Warmaiden helps clear waves faster but she probably is dying anyways. Scyl and apo should keep you alive.  Some accessories will help your stats too (can u do spider13 yet).  Want to get acc over 200.

you need better gear too 

 Hello @djs078  

To face the challenge of stage 20 you must meet certain
stats thresholds; we will list those stats and then get into individual builds
as we can see a lot of room for improvement 

ACC - this stat, for champions who need their debuffs to
land, must be 200 minimum, ideally in the range of 230-250. this is due to the
boss having 200 res 

Speed -  

you want your champions to lap the waves as well as the
boss so that they can remain well sustained and perform adequate dps. since you
do have apo as booster this threshold is lowered, however, using the boost and
speed buff to go even faster than just lapping once is recommended, the speed
ranges we are referring to would be the 200 speed mark 

Champion pick order and aura  

Use kael's hp aura  

pick order (kael/apo/mm/ninja/warmaiden) 

now we will go over individual champion builds 

Ninja  

priority stat in this case is to have his accuracy meet
the threshold.  

this way his a3 will keep waves locked and have him
utilise his a2 on the boss for major dps  

mm 

mm needs to meet the speed threshold as well as the acc
threshold 

this way he can cycle his cc skills, sustain skills 

kael  

he should be in your starter lifesteal dps set,  

needs to be capped crit rate ideally, so that you can dps
the waves 

both warmaiden and apo are well built in comparison to
the other champions  

best of luck! if you have any more questions let us know  

kind regards 

Ophe  

Thank you all for the helpful responses. I will spend a few more weeks farming stage 16 to see what kind of improved gear I can get and then I will start following some of the suggestions here. Much appreciated!

Good luck! Let us know how it goes. :D

So  here's  a  quick  update: I farmed Dragon  16  and  Spider  10  to  aquire  better  gear  while  also  getting  full (or  nearly  full) masteries  for  my  Dragon  20  team.  I  used  the  HH  team  recommender  and  ended  up  running  Frozen  Banshee  lead  followed  by  Scyl,  MM,  Ninja,  and  WM.  I  used  my  aquired  dragon  and  spider  gear  to  get  everyone  to  min  200  acc,  170  spd,  and  30k-40k+  hp.  Long  story  short,  this  team  successfully  beat Dragon  20  100%  of  45  runs  on  auto,  although  it  takes  around  4:00  per  run.  It's  a  start  and  now  I'll  work  on  farming  the  stage  for  a  few  more  weeks  to  get  better  gear!

When you can, drop MM from the team. He's basically dead weight. You need him for now for survivability, but in the long run you won't.

Frozen Banshee, with the proper gear, can solo Dragon 20, so you just need champs to get you through the waves. Dropping MM for another wave nuker would prob speed things up - eventually.

Makes sense. I  have  been  working  on  building  Frozen  Banshee  well  and  you're  right,  she  basically  solos  the  dragon  and  i  have  my  time  down  to  around  3:13.  I  finally  pulled  my  last  champ  needed  for  Rhazin  so  I'm  going  to  focus  on  finishing  his  fusion.  Is  he  a  viable  substitute  for  MM  in  my  dragon  comp?

I  am  also  about  to  6-star  Royal  Guard  for  some  help  in  the  Spider  Dungeon  as  well  as  CB  potentially.  I  can  2 -key  brutal  and  I'm working  on  a  team  to  get  me  to  2-key  NM. I  have  a  lot  to  choose  from  for  my  CB  comp  including  Coffin  Smasher,  Sepulcher,  and  Sandlashed. It  seems  like  Rhazin  and  Royal  Guard  could  have  roles  there  as  well.

 I  also  pulled  Burangiri (I'll  use  in  DT) and  an  additional  Gnarlhorn  so  I'm  all  over  the  place  and  need  to  figure  out  the  best  comps  for  each  area.  

I would say Rhazin is better than MM, yes, but I wouldn't say much better. Royal Guard, on the other hand, would be a *great* addition to the Dragon 20 team - provided you can survive. Once your team gets strong enough to replace MM's defensive abilities, 100% swap him out for RG.

For CB, I'd start another thread, but you're definitely on the right track.