I've migrated all of my decklists to Moxfield and stopped updating them here.
Please find this decklist at: https://www.moxfield.com/decks/WxBo4W0vHkWPq3bz0FYfWQ
Decklist updated: 07/13/2021
Description updated: 09/04/2020
Power Level: ~7.5/10
I wanted to build a Merfolk deck for edh, but I wanted it to be Bant. After going through the list of all commanders, I decided on using Derevi, Empyrial Tactician as my commander because he allows for some tap shenanigans that merfolk love so much, as well as providing some much needed flying defense and providing me with Bant color identity.
That being said, this deck is a Merfolk tribal combo deck with a wizard subtheme, and is built heavily around tapping and untapping my permanents.
The primary win conditions of this deck are the five combos that follow:
1) Prioritize getting Azami, Lady of Scrolls, Stonybrook Schoolmaster, and Intruder Alarm out. You use Azami's ability to tap Stonybrook Schoolmaster to draw a card, which creates a 1/1 merfolk token that triggers intruder alarm to untap Stonybrook Schoolmaster. You repeat this process until you have drawn your deck, then you play Laboratory Maniac and proceed to draw one additional time and win the game, or cast Thassa's Oracle with no cards left in your library for the same win.
2) This combo is very similar to the first one but it utilizes different cards. Once you have Thrasios, Triton Hero, Forbidden Orchard, Intruder Alarm, and Kiora's Follower out you may proceed to combo. You first tap Forbidden Orchard to create any color mana, and give the 1/1 spirit to any opponent. This triggers Intruder Alarm's ability. With that trigger on the stack, use Kiora's Follower to untap your Forbidden Orchard. Then the trigger resolves and untaps your Kiora's Follower. You repeat this process to get infinite mana. Then use that infinite mana to activate Thrasios, Triton Hero's ability multiple times to draw your deck, then play Laboratory Maniac and proceed to an additional draw and win, or once again you can use Thassa's Oracle here instead.
3) Finally, the third combo is basically a mix of the previous two. You need Cryptolith Rite, Intruder Alarm, and Stonybrook Schoolmaster (Stonybrook Schoolmaster must not be summoning sick). With these cards, you can generate infinite colored mana as well as an infinite amount of 1/1 blue merfolk wizard creature tokens. From there, having Thrasios, Triton Hero gets you all the lands from your deck to the battlefield, and every other card in your library to your hand. It is then easy to cast Laboratory Maniac and then activate Thrasios, Triton Hero an additional time to win the game (or Thassa's Oracle).
4) Is the simplest combo, utilizing Helm of Obedience and Rest in Peace. Once you have both out, you can activate Helm of Obedience for X=1 and then because the card they mill gets exiled to Rest in Peace, it will mill their entire library, making them lose during their next draw step. This will kill one opponent each time, but coupled with Derevi, Empyrial Tactician's ability to untap permanents, you could easily stack 2 untap triggers on the Helm of Obedience and then tap it for X=1 targeting a different opponent each time between the untap triggers to mill out all of your opponents.
5) You can also take infinite turns and kill everyone through infinite combat steps by using Wanderwine Prophets. As long as that creature can connect with an opponent, easily done via island walk or Merfolk Sovereign, you get infinite turns if you have Stonybrook Schoolmaster and Derevi, Empyrial Tactician or Cryptolith Rite, or really any way to tap down a creature at will. For the purposes of this explanation I will assume you are using Derevi, Empyrial Tactician's trigger to tap. When the Wanderwine Prophets connects, you get a trigger to sacrifice a merfolk for an extra turn and an untap/tap trigger. Use the tap trigger first to tap down Stonybrook Schoolmaster, creating a 1/1 merfolk token. Then resolve the Wanderwine Prophets' trigger and sacrifice the token merfolk, gaining an extra turn. Repeat this process indefinitely to close out the game.
Something important to note is that four of the five combos are relatively easily interrupted by a timely Krosan Grip, so watch your opponents open mana on your turn before attempting to combo out.
In the case that the combo gets interrupted or a piece gets exiled, you can always win with all of the island walk and lords in the deck (Lord of Atlantis, Master of the Pearl Trident, Merfolk Mistbinder, Merfolk Sovereign, and Mirror Entity to kill your opponents in blue or even those not in blue by using Aquitect's Will.
This deck is for a 75% power meta, and could easily be improved with some tweaks to fit your meta. The overall goal of the deck is to have fun, and I have been enjoying playing this deck immensely.