-3 Chaos Hunter
. You want Ophion out as much as possible, with him out you cant even summon this.
-1 Pot of Avarice- You want monsters in your grave as food for Kerykeion and because of his effect you don't often have a very full grave
-1 Dimensional Prison- its meh this format, lots of popping effects.
+1 XYZ reborn- For the virus i'm going to suggest next.
+2 Eradicator epidemic virus- This things so good against most of the big hitters this format (screws over things like Prophecy really badly and things like DW take huge hits too) great card and with the Xyz Reborn
its like Ophion never left.
+1 Reinforcement of the Army- Gets you Castor which is always nice. Gets you any Lswarm if you got Infection out
+1 Forbidden Dress
/Bottomless- Your call, both are good cards just what you like more..Personally I dropped down to 2 veilers and run 2 BTH here.
Extra needs some work
-2 Steelswarm Roach
...Whats the point Ophion does it better.
-1 Utopia Ray- Not needed...I don't even think Utopia's needed but thats not something i'm suggesting just a personal preference.
+1 Blackship of Corn- Things the nuts. Gets rid of so many issues. (it sends not destorys so zenmaines and that kinda stuff cant block it)
+1 Gagaga Cowboy- Basically a 3ker when need be and you'd be surprised how often you can use his second effect to win games.
+1 Abyss Dweller- kills mermail, kills dark world just a good side card
Now as a side note I'd drop Thanatos I just don't think hes very good honestly...Something like Catastor would be better there (since you run all rank 4s and veilers a 1 tuner) since he can get over things here and there when needed....But that ones your call as thats preference not advice.
As for your side...Well I usually don't comment too much as it depends on your meta..but since this deck isn't out yet ill assume its a DN deck. so
+2 Droll and lock bird- Screws over any mass draw deck
+2 Thunder King Rai-oh- Screws over like...all the meta.
+2 Dimensional Fissure
- Better than Macro here since your XYZ materials don't get banished
+1 MST- Should always have 3 split between main and side
+2 Deck Devastation Virus- Easy to use with a tonne of your XYZs and hurts so many decks
+2 Gozen match- Hurts the dragons hurts...alot
+2 Soul Drain- Mermail/Darkworld
theres 13. rest are up to you. I side those and 1x Evilswarm O'lantern for decks where i need a pop effect (since evilswarm have next to no pop abilities) and 1x Forbidden Dress
(since I main 2) For decks that have alot of pop effects.
Theres my tips...take em or leave em