Difficulty

Difficulty in Risk of Rain 2 can refer to two things : Initial difficulty and Scaling difficulty

Initial Difficulty
Initial difficulty in Risk of Rain 2 is selected along with the character before starting a run. The three difficulties are Drizzle, Rainstorm and Monsoon.

Drizzle.jpg Drizzle
Drizzle is an easier difficulty designed for a more relaxing experience.

Time affects scaling difficulty at 50% of the normal pace.

Players have a +70 bonus to armor.

Monster Logs will not drop, although achievements and their unlocks can be still earned normally.

Rainstorm.jpg Rainstorm
Rainstorm is the default difficulty of the game.

Monsoon.jpg Monsoon
Monsoon is a harder difficulty designed for players who seek a challenge.

Time affects scaling difficulty at 150% of the normal pace.

The Deicide achievement can only be earned on this difficulty.

Scaling Difficulty
Scaling difficulty is a core mechanic of Risk of Rain 2. As a run progresses, the difficulty will steadily rise, making enemies both stronger and more numerous.

The steadily rising difficulty is represented in-game by a bar on the top right corner of the screen. This bar shows the selected initial difficulty, the current run timer and the current status of the scaling difficulty. As the bar progresses, it will pass through multiple named difficulties :


 * Easy


 * Normal


 * Hard


 * Very Hard


 * Insane


 * Impossible


 * I SEE YOU


 * I'M COMING FOR YOU

The HAHAHAHA difficulty is endless, although enemies will keep leveling up and the difficulty will keep rising even if the changes are not visible on the bar.
 * HAHAHAHA

In addition to the increase over time, every time a stage is completed, the difficulty will jump forward, which will cause a spike in difficulty, and the bar will also increase faster. This increase is exponential, which means that as more loops are completed, the game becomes exponentially harder.

Effects of difficulty
Each of these named difficulties contains two intermediate "notches". Every time a "notch" is reached or the next named difficulty is reached, enemies will level up, which is indicated by a visual effect and a level-up sound similar to a player level-up, although with a lower pitch. Just like players, enemies gain 30% Health and 20% Damage (Compared to their base values shown in the Logbook) per level.

In addition to enemy levels, the difficulty also affect the spawn rate of enemies. As difficulties progress, enemies will spawn faster and in greater numbers. After a while, stronger enemies will start to spawn out of Teleporter events, including Mini-bosses at first (such as Greater Wisps) and even Teleporter bosses (such as Stone Titans). Higher difficulty also increase the frequency of Elites, stronger enemies with additional abilities.

The final effect of difficulty is the cost of interactables. When reaching a new stage, the cost of chests, shrines of chance, turrets, etc. is calculated relative to the difficulty.

Multiplayer
The rules for scaling difficulty do not change in Multiplayer, however, two numerical changes are applied : Unlike the first game, playing multiplayer solo (Starting a server but not waiting for other players) will not change the scaling compared to "true" singleplayer.
 * The initial difficulty is higher, although this is not reflected on the bar. This is why the spawn rate is higher and chests are more expensive. Enemies still start as level 1 however.
 * Time has a greater effect on scaling difficulty (The bar advances faster). This is reflected on the bar, although the effect is subtle for a low player count.

The math of scaling difficulty
The effect of difficulty on the game is centralized in a global number called the difficulty coefficient (Or coeff for short). This coeff is constantly re-evaluated and it is calculated as follows :

$$playerFactor = 1 + 0.3 \times (playerCount - 1)$$

$$timeFactor = 0.046 \times difficultyValue \times playerCount^{0.2}$$

$$stageFactor = 1.15^{stagesCompleted}$$

$$coeff = (playerFactor + timeInMinutes \times timeFactor) \times stageFactor$$

In these formulas,


 * playerCount is equal to the number of players in the game (This includes disconnected players).


 * difficultyValue is equal to 1 for Drizzle, 2 for Rainstorm and 3 for Monsoon.


 * stagesCompleted is equal to the number of stages completed (Includes the Celestial and Gold portal areas but NOT the Blue portal area) - this is the same number that shows up in the statistics screen at the end of the run.


 * timeInMinutes is the amount of minutes since the run started, incremented every second.

Therefore, in non-modded lobbies, the coeff will start at an initial value of 1 to 1.9 depending on the number of players. The bar will then progress linearly as time increases, going faster for a higher difficulty or player count. Every time the players enter a new stage, the coeff increases by 15% of its current value, which causes the jump on the bar.

It is interesting to note that although named difficulties do not have any tangible effect on gameplay, they do signal an increase of the coeff by 1 (Actually 0.99 but by the time the difference becomes significant, the difficulty is already HAHAHAHA). In singleplayer for example, Easy represents a range for the coeff of 1 to 2, Medium 2 to 3, etc.

Effect on enemy level
The enemy level is calculated using this formula :

$$enemyLevel = 1 + (coeff - playerFactor) / 0.33$$

No matter the number of players or difficulty, this means that enemies always start at level 1. As the coeff rises however, so does the enemy levels, and the faster the coeff increases, the more the effect becomes pronounced - especially when looping, as the exponential rise in the coeff is translated to enemy levels and therefore stats.

Effect on money costs
Whenever a stage starts, the cost of an interactable is derived from the following formula :

$$moneyCost = baseCost * coeff^{1.25}$$

The base cost is equal to what the interactable would cost in the first stage of a Singleplayer run (For instance the base value of a chest is 25$). Since the coeff starts higher in multiplayer, this is why chests are more expensive.

Effect on spawn rate
Spawns are managed by the Combat Director, an advanced system that is responsible for spawning a variety of enemies matching the difficulty. The way the Director spawns enemies is pretty complex, but the global overview is this :

As time goes on, the Director accumulates a number of "credits" that is directly proportional to the coeff (For instance, doubling coeff means doubling the credit income). Regularly, the Director will pick a random enemy to spawn depending on the stage spawn lists and spend credits to spawn a group of up to four. Weaker enemies such as Lemurians have a low cost while bosses like Magma Worms have the highest, with Elite enemies costing 6 times the cost of the regular enemy.

This means that when the coeff is low, the Director will only spawn lone, weak enemies. As the coeff rises however, so does the Director's budget. This allows it to spawn larger groups of enemies, stronger enemies, more Elites, etc

The director will also avoid spawning an enemy group that is "Too cheap" for its current credit. This is why as time geos on, weaker enemies are less and less common and even disappear completely after a while. This also means that for particularly deep runs, the coeff becomes so large that even bosses become too cheap, which causes strange behavior such as Teleporter bosses not spawning, eventually culminating into completely empty maps as coeff reaches into the thousands, as the Director endlessly accumulates credits it refuses to spend.