A take on the Rain archetype with which I climbed from rank 3 to Pro this season - 25-10 score.

If the question is why Madoc, the answer will be why not :). In the end you have to have fun, even if the deck is not the most optimal and best you can use/find. On a serious note, Madoc helps with thin, and bombs help with control - something I find rain decks often lack and hey oppo can't eat/banish everything :P. I'd add suggestions at the end to improve or make the deck better even without Madoc.

Other cards besides Madoc that help with thin and draw are as follow - Rioghan (he starts in your graveyard, making your deck essentially 24 cards), Oneiromancy, Coral and Birna with Skirmisher discard package. That totals in 6 card. The extra discard you might end up with, can be - usually is - a card you don't need, or to find something better when you have to.

A huge part of Rain decks that utilize Rioghan is using him as big finisher if you accumulated a good amount of Rain (or Storm) on opponent rows. Coupled with Messenger of the Sea or two on board it can result in a huge swing/come back.

With that, cards like - Melusine, Covenant of Steel (defender), and triple reanimate/play/summon card from graveyard - Fucusya, Sigrdrifa's Rite and Bride of the Sea - are vital to your success. You shouldn't be afraid to use defender and Melusine (depends on match up) - even as starters - as long as you have the chance to bring them back.

Melusine plays a central figure as one of your most important rain engines and carryover - because she gets +1/2 hit-points/power if there is unit/s next to her. When you revive her they are kept (due her veil status, you can bring her back from graveyard multiple times)!

The cards you play with her/next to her are - Drakkar - preferably to the right of Melusine, it can also protect Defender if you don't want it to combo it with Melusine! Hermit and Havfrue Singer are great combo as well. Hermit to the left of Melusine, Singer to the left of Hermit (sometimes on a different row if you don't want to fill it). Reason for that is because Melusine damaging Hermit makes it so he heals each turn which activates Singer ability. Hermit also allows you to use Melusine order each turn because he is a Cultist. If it dies, Singer also have the same tag and can take over the duties! Melusine Cultist is the last "Sea Goddess" order activator and can make you additional 2 turns of rain, plus the added advantage to boost unit to the right if there is rain on the opposite row and it survives. Don't underestimate that little advantage!

The last few cards that fill the package are Little Havfrue - good 4p unit that also can make rain, be pro-active play or just a discard target if you miss on Skirmishers. Freya's Blessing is and can be often important card to bring back a cultist for Melusine, Messenger of the Sea (don't be afraid to sacrifice one due that) or just what you might need. In worse case scenario it is also Bride of the Sea target if you miss on Sigrdrifa.

Rage of the Sea leader helps with Rain and is good way to end game with Bride of the Sea->Sigrdrifa->Rioghan (especially if you lack Rain) and have a surviving Messenger.

Gameplan

R1

Try to look for at least one bomb to get Madoc (sometime it's smart to wait), Discard package with Coral and Birna, Defender, Melusine, Oneiro if one of latter 2 are missing. You can fight the round if Defender and Melusine are not answered or played at point they can't be. If a cultist combo is there and a Messenger is safely getting value with Rain each turn - it's tough for oppo to keep up. As mentioned 1 Messenger sacrifice is fine (but depends on match up). In some situations you'd need to make up your best with bronze cards and a few bombs. The possibility of Madoc damaging, getting back with each bomb and clearing units can scare your foe.

R2

Depending on situation. You prefer R3 and even long rounds. If your Melusine got a lot of carryover and you have a great hand/are facing opponents that do better or make you worse in R3 - you can definitely push.

R3

If you played Defender and Melusine in previous rounds and kept your cards that can bring them back, do so as soon as you can. My advice as to how you should use your resurrection cards is in order - if defender and Melusine are in graveyard - Sigrdrifa->defender, Fucusya->Melusine (if you can take advantage of her repeatable order it pays off), Bride->Rioghan to finish. Try to set up cultist combo with Melusine. If Defender survives it's worth sacrificing points that Melusine does to something else, so defender is kept healthy. Otherwise if no important card to resurrect - same strategy - set up Mesuline, but plan on what else you might bring back from/ends in graveyard! In this case Fucusya can bring 4/5p unit with a ton of Rain value! Messenger of the Sea should be played according situation - if it's safe behind defender - early, if it's not, as your last couple of cards. Try to get Rain on both rows if there is units on them. You don't need a huge amount of rain on both rows to get value or make a comeback with Messenger and Rioghan as a finisher.

Disadvantages

Well, it's a Rain deck and if your Rioghan is banished, that's a lot of power lost down the drain. Your hope is to keep Melusine as active engine and stick an early Messenger. If Melusine gets banished, your defender is gone, Rioghan eaten and Messengers dealt with/didn't get value, then you most likely lose.

Be careful of Madoc Cataclysm replacing Rain weather effect or the other way around. It doesn't happen often, but think which one will be more important if it occurs - they don't stack.

Suggestion to improve/tinker with deck

You can cut Oneiro and try out Royal Decree. That way you gain 4 extra provisions man! On the negative you lose a bit of consistency - if you didn't draw Sigrdrifa, you can't tutor her. With the extra provisions you can upgrade some cards or bring better/more bombs, a Svablod Priest that's also great with Melusine. Other option is cut out on Madoc (and have 1 less thin) and bring different control with Heatwave, a Squirrel, Gutting Slash and Lock/Delirium/More removal/Priest. If you take the suggestion for Royal Decree instead Oneiro - you get even more options - be that purify/banish/lock at 6p etc.

Overall

It's not an easy deck to play or master and highly likely take time to learn. A lot of small calculations are required almost every turn and that can tire you out, because they do become complicated with other effects and abilities to consider. It's a peculiar one, but still, when you start getting the hang of it, it's also very rewarding!

Thanks for reading and have fun!