D2 Combat System

D2 Megaten's combat is based on Shin Megami Tensei III: Nocturne, with changes to support "clicker game" friendly combat and easier auto-battle flows.

At a high level, the system inherits key elements of press turn:

• Each demon has defined elemental strengths and weaknesses, which can be patched with skills.
• Attacks that exploit elemental weaknesses generate half press turns.
• Critical hits generate half press turns.
• Missed attacks lose extra press turns.
• The base stats for each demon are strength, magic, vitality, agility, and luck.

Differences exist to encourage the use of magic and defensive builds, as well as to correct some oddities about the swingy nature of Nocturne's combat:

• Hitting a weakness or landing a critical hit on a half press turn does not generate a half press turn.
• There are typically no "load bearing" demons or characters.
  • Alter World is the sole exception for the player, where each mode has a protagonist deployed with their demons that can be equipped with fused armor and weapons.
  • Outside of Alter World, the only demons that can be individually defeated to win a battle are the Aura Gate bosses.
• A rare, stronger class of critical attacks known as "death blows" does not exist in this game.
  • The closest is a "charged" physical attack that lands a critical hit, which requires consuming the Charge skill in a prior press turn.
• Physical attacks now use MP instead of HP.
• Each demon has a small pool of up to 10 mana points that replenishes by 3 or 4 points on the demon's press turn.
  • Mana pools reset to 10 mana points at the start of PvE combat, and 5 mana points at the start of PvP combat.
  • As there's no need for a central location to recover all mana points, there's less of a risk in using magic.
  • The recharge rate forces the player to use high cost skills less frequently, in absence of a demon with an MP replenishing passive or an equippable armor set (brands) that enhances the rate of recovery.
• Unless the magic skill specifically indicates that it can do so, magic cannot miss or cause critical hits.
  • Physical attacks are still known to potentially crit or miss, depending on accuracy and critical rate.
• Light and dark magic skills no longer innately have a chance of instantly killing the target.
  • Instant death skills are now treated similar to status ailments, falling under their own "mortal" classification of skills.
  • Some demons possess unique buffs or passive abilities that can null all mortal skills.
• There are dedicated defensive statistics for physical and magic resistance, which can be patched with skills and equippable armor known as brands.
  • Infamously, Nocturne lacks dedicated defense stats, unlike prior games, leading to more "swingy" combat as offense, speed and chance are prioritized.
• Luck does directly influence critical attacks, chance to miss, and ailment recovery, where in Nocturne it was largely an ignored stat.
• Demons, especially gacha demons, can have unique passive skills to further distinguish their impact on combat.
• Offensive, defensive, and accuracy buffs only have one support level up or down from the baseline, and last for the fixed number of turns indicated by the skill.
• Demons cannot be summoned or returned within combat.
  • In Aura Gate, the player has two groups of demons to switch between without exiting the dungeon. Demons cannot be healed outside of combat without exiting the dungeon.
  • The party of demons can only be fully adjusted outside of combat, and outside of a dungeon.
• Each demon has only two slots to equip skills to.
  • Base two to five star demons have three fixed skills and base one star demons have only two.
• All demons have an additional skill that is tied to their color.
  • Common (grey) demons are fixed at one skill that cannot be changed
  • Summoned gacha (colored) demons can choose between four different skills, each tied to a color, best suited for their build. Transferring between colors requires consumable items.
• A rare, expensive consumable known as transcendance motes can allow for further skill customization.
  • If a sufficient number of expensive transcendence motes is applied to a type of demon, they can have up to three switchable skill slots, based on the transferrable skill slots available, to change equipped skills without consumables.
  • The most expensive type of upgrade gives the demon one additional transferrable skill slot, which can be made switchable in a follow up upgrade.
• Each party of up to four demons is assigned one playable Dx2, who confers a series of buffs to each demon in the party with a unique set of passives.
  • Most of these are small in the greater scheme of things.
  • The most interesting are the random skills, e.g. Jeng Yun's ability to sometimes go first despite his party's speed rating and Ririn's chance for a full press turn when a randomly hitting skill lands the maximum number of possible blows.
  • The Aura Gate heroines have unique passives to reveal map locations on entering a floor, though Xana's is somewhat notorious for messing up the auto-move AI.
• Any demon can use items during their turn, at the cost of one press turn.
  • There is one playable Dx2, Rika, whose cost for using items is reduced to half a press turn.
• "Auto mode" in combat no longer simply repeats the previous action assigned to a demon, but instead has the AI fight the battle for you.
  • This often works surprisingly well with only a few poor decisions made when the enemy is at low health.
  • Manual mode is often needed to survive harder battles that need specific inputs.
  • The "auto mode" AI never uses items, it exclusively relies on the skills available to a demon.
  • The AI for each demon can be configured to prioritize attacking, buffs, or healing.

For more details, the community supported Dx2 Wiki has formulas behind the combat based on data mining and speculated information available.

This is further expanded upon in later modes such as the various Alter World quests, rogue-like dungeon and PvP modes, along with gacha demons that have introduced yet more new types of passive effects to the game's combat.