Mana Base Analysis - Replenish Guide

The Math of the Mana Base

Based on the mathematical concepts from Frank Karsten's Magic Math video, we can analyze the Replenish mana base through hypergeometric distribution to balance the risks of mana screw and mana flood.

Core Benchmarks

To function well, a deck must aim for a ~90% probability of dropping its third land on turn 3, and a ~75% probability of having its fourth land on turn 4. Playing exactly 25 lands perfectly aligns with these metrics.

However, "mana hungry" control decks that desperately need to ensure a 4-drop resolves on time should push to 26+ lands to elevate that 75% benchmark. A deck can only skip this rule if it compensates with enough cheap card draw or alternative mana sources.

25 vs. 26 Lands: Hitting the Curve

Lists split about evenly between 25 and 26 lands. Because what matters most is reliably hitting your key curve turns (3 and 4), here is how both builds compare:

Metric	25 Lands	26 Lands
Turn 3 (OTP)	~81.9%	~84.6%
Turn 3 (OTD)	~88.1%	~90.2%
Turn 4 (OTP)	~67.5%	~71.6%
Turn 4 (OTD)	~76.6%	~80.2%

Note: These probabilities calculate raw land drops. While Ancient Tomb acts as two mana and dramatically improves your odds of casting a 4-drop early, it is safest to build your mana base assuming you won't always draw it; consider that you only have a 52.8% chance to draw one by turn 4 on the play.

However, because current lists omit City of Traitors to focus on grinding out attrition games, the 25-land version protects you slightly better long-term against flooding. The 26-land version accepts that late-game flood risk to minimize early stumbles.

Key Lands Analysis

Ten Basics

10 Main (5 Island · 5 Plains)

The mathematical model assumes a golden rule: your lands stay on the battlefield. If an opponent destroys a land with Wasteland early, your 90% probability of early development instantly collapses.

Playing 10 basic lands (Five Islands and Five Plains) and strictly opening with basics ("Turn-One Sequencing") is the safest way to avoid early game blowouts. It allows you to play around Wasteland and Price of Progress if required. Getting your first two or three land drops as basics matters a lot against burn and mana-denial decks, ensuring you stay alive long enough to cast your powerful 4-drops.

Ancient Tomb

4 Main · 100% Inclusion

Ancient Tomb is your primary accelerant, completely altering your deck's early-game math. By generating two mana from a single drop, it shifts your core requirement from needing four physical lands to just three.

Since the probability of hitting your third land drop by turn 3 is a massive ~90%, Tomb often turns an otherwise shaky opener into an easy keep, allowing you to bypass the turn 4 bottleneck entirely and cast your most impactful spells a full turn early.

It powers out a turn-two Intuition or Frantic Search. It lets you land turn-three combo pieces like Replenish or Opalescence ahead of curve, all without skipping a land drop (keep in mind that for a turn-three Opalescence or Wave, you'll specifically need a Skycloud Expanse and a Plains alongside the Tomb to cover the double white).

Additionally, untapping Ancient Tomb with Frantic Search nets you an extra mana (usually a white one), which fuels big turns and helps you dig when you're otherwise starved for mana.

Skycloud Expanse

3–4 Main · 99.4% Inclusion

Your main fixer—it turns colorless mana from sol lands and basics into blue or white. To cast double-pipped four-drops on time, color filtering is crucial.

Build Configuration	2+ sources by turn 4
25 lands (16 sources)	~81.7%
26 lands (17 sources)	~84.7%

This is why the 26th land slot could go to a Skycloud Expanse or an extra Plains. There is no point in increasing your probability of drawing 4 lands if you don't equally increase the probability of having . On 25 lands, players usually run only three copies of Expanse to keep as many basic lands as possible.

Why Not City of Traitors?

Omitted from Maindeck

Without Parallax Tide to close games out fast, post-ban Replenish leans on grinding into the mid and late game. City of Traitors makes your sequencing painful and quietly costs you board presence in long attrition games.

Turn-One Sequencing
As a general rule, lead with a dual land to keep your color options open for whatever you draw turn two. But if you think your opponent has Wasteland, lead with a basic instead so you don't get blown out on tempo.

Ready for the post-board games? Head to the Sideboard Guide to see how to adapt your 60.