Accessors can be acquired from the accessor quests. You equip them on your units to gain an additional passive effect—they're essentially another ability.
An accessor's effect only affects the unit who has the accessor equipped, unless it specifies that it is for all units (全体). Example: 攻撃力UP (attack up) vs. 全体攻撃力UP (all units attack up).
Available accessors range in quality, up to S++.
Possible effects:
- End-of-turn HP recovery
- Flat stat increase: HP up, attack up, recovery up, or defense up
↳ Accessors of this type most commonly provide a buff only to the unit they're equipped to, but there are S++ accessors that buff all units (excluding HP). - Counter
- Panel conversion, e.g. “Green panels drop as red panels”
- Easier crash panel creation: the minimum number of panels needed to create CPs or SCPs is reduced (to a minimum of 0 and 1, respectively)
↳ There is an S++ accessor of this type that affects all units. - Bomb size increase
- Attack participation: the unit joins normal attacks at x% power when they aren't in the front
↳ This effect does not stack, and skills and abilities are prioritized over accessors. So, if your unit is already joining attacks due to a skill or ability, equipping an attack participation accessor will have no effect, even if it has a different damage multiplier. (Details) - Killer damage: increased damage when attacking a specific kind (human, demon, god, animal, machine, dragon, or unknown)
- Skill turn reduction
- Stat increase when a skill is used. Also changes the BGM to one of around 60 possible songs
- Accel chain
An exhaustive list of accessors is available on the official wiki here. The list includes limited-time accessors that are no longer obtainable (e.g. the 2022 Valentine accessors), where they come from (accessor quests, traversal quests, an event…), and descriptions of the effects.
If you obtained accessors when they were first implemented (back when they had a trigger chance), they'll have become “β” accessors with end-of-turn HP recovery or a flat stat increase instead. The 2020 accessors also had their buffs halved (from 2020 to 1010).