Requiem is a gameplay overhaul for vanilla Skyrim and it forms the baseline of Lorerim's mechanics. It touches almost all aspects of the gameplay of Skyrim in several ways, as detailed below
Arguably the most significant change that Requiem makes to Skyrim is develeling the world. What this means is that enemies no longer scale to the players' level (at least not to any significant degree). In practical terms this means things like Vampires, Dragons, and even Draugr are much more deadly to an unprepared low level character, and are essentially "gated off" until the player is ready.
Like in vanilla Skyrim, whenever you level, you increase your base Health, Stamina, or Magicka. What is different in Requiem however is that each of these three attributes governs a variety of other mechanics, including things like Carry Weight, Armor Penetration, Movement Speed, Attribute Regeneration, Unarmed Damage, etc. See the included chart below for more specific numbers.
One of the more significant changes that Requiem makes to the core gameplay mechanics is in regeneration of attributes. By default, health regeneration is disabled, and stamina/magicka regeneration are significantly reduced. This is designed to make leveling, gear, perks, etc all much more impactful.
Damage in Requiem is scaled much higher than in vanilla Skyrim, and as such the world is much deadlier (both for the player and enemies). It is not uncommon for a low level player to die in one hit to certain attacks.
Similar to vanilla Skyrim, Armor in Requiem reduces incoming damage from melee attacks by a certain percentage. This is much more significant in Requiem however as damage is much higher.
Requiem introduces a new mechanic called Armor Penetration. Each point of Armor Penetration reduces enemy armor by the corresponding percentage. This is a critical mechanic for anyone practicing melee or archery as many enemies have very significant armor ratings.
In Requiem, Skill Rating is much less significant to its corresponding skill. This is to allow Perks themselves to shine, which are the cornerstone of character building in Requiem.
Lockpicking has been overhauled in Requiem to require something called "expertise". Locks require a corresponding amount of expertise before picking can even be attempted. No longer can a level 1 character open any lock in the game by cheesing the minigame.
In the table below: M, H, S stand for base magicka, health and stamina, respectively, while Z typically represents a weighted average. Also, sqrt{} stands for the square-root.
Derived Attribute
Formula
Attribute 'Z'
'Z' Break Points
Bonus to DA
Magic Resistance
sqrt{Z - 150}
M
175 --- 250 --- 375
5% --- 10% --- 15%
Magicka Regeneration
8x sqrt{Z - 100}
M
125 --- 200 --- 325
40% --- 80% --- 120%
Stamina Regeneration
8x sqrt{Z - 100}
S
125 --- 200 --- 325
40% --- 80% --- 120%
Movement Speed
(3/4)x sqrt{Z - 125}
(H + 4S) / 5
141 --- 190 --- 270 --- 381
3% --- 6% --- 9% --- 12%
1H Damage
4x sqrt{Z - 150}
(H + S)/2
175 --- 250 --- 375
20% --- 40% --- 60%
2H Damage
4x sqrt{Z - 150}
(4H + S) / 5
175 --- 250 --- 375
20% --- 40% --- 60%
Bow/Xbow Damage
4x sqrt{Z - 150}
(H + 4S) / 5
175 --- 250 --- 375
20% --- 40% --- 60%
Unarmed Damage
4x sqrt{Z - 110}
(H + S) / 2
135 --- 210 --- 335
20 --- 40 --- 60 (no %)
Carry Weight
4x sqrt{Z - 110}
(4H + S) / 5
135 --- 210 --- 335
20 --- 40 --- 60
Poison Resistance
4x sqrt{Z - 140}
(3H + 2S) / 5
165 --- 240 --- 365
20% --- 40% --- 60%
Disease Resistance
4x sqrt{Z - 100}
(2H + 3S) / 5
125 --- 200 --- 325
20% --- 40% --- 60%