Larian Studios Forums Baldur's Gate III Baldur's Gate III - Help Tips & Tricks Mobile Feat - how does it work?

I searched and could not find. If already discussed, please delete and kick me in the right direction

I didn't read the in-game info about Mobile at lvl4 and am stuck with the fexwiki entry which I find ambiguous.
Your speed increases. When you use the Dash action, difficult terrain doesn't slow you down. Moreover, if you move after making a melee attack, you don't provoke an opportunity attack from your target.
I have no issues with "When you use the Dash ... " or "you don't provoke an opportunity attack from your target ... ", even if the wording of the latter does not rule AoP from NON-TARGETS (I've played WFB/WH40K and I know a lot about poor wording of rules and RAW arguments ... :().
I'm confused by "Your speed increases" - is that "pure fluff" or does it raise Racial Speed? The Smol Races move 9m? Others boosted to 10,5m? Wood (Half) Elves move 12m?

Formally, the feat is meant to increase your speed by 10ft, as a permanent boost.
The feat not protecting you from opportunity attacks except from those that you make melee attacks against first is the intended function and the wording is correct and accurate.

Thanks!

The terrain doesn't slow you down is the key part imo

I'm not sure that's 100% the case. I think the terrain not slowing you down only applies to dash actions (no idea if it's meant to apply to a rogue's dash bonus action)

It should do, formally speaking: the Mobile feat applies its difficult terrain effect "When you take the dash action"; the rogue feature lets you take the dash action as a bonus action, but you are still taking the dash action, so it still applies.

If the designers had wished to restrict the mobile feat to only applying to full actions, the language they would use would be: "When you use your action to dash," or "When you dash as an action," - a small difference in wording, but not a frivolous one.

The mobile feat unlocks three passives (as per patch 9): Mobile_PassiveBonuses;Mobile_CounterAttackOfOpportunity;Mobile_DashAcrossDifficultTerrain

new entry "Mobile_PassiveBonuses"
type "PassiveData"
data "DisplayName" "Shared_Passive_Mobile_PassiveBonuses_DisplayName"
data "Description" "Shared_Passive_Mobile_PassiveBonuses_Description"
data "DescriptionParams" "Distance(3)"
data "Boosts" "ActionResource(Movement,3,0)"

new entry "Mobile_CounterAttackOfOpportunity"
type "PassiveData"
data "DisplayName" "Shared_Passive_Mobile_CounterAttackOfOpportunity_DisplayName"
data "Description" "Shared_Passive_Mobile_CounterAttackOfOpportunity_Description"
data "ExtraDescription" "Shared_Passive_Mobile_CounterAttackOfOpportunity_ExtraDescription"
data "Icon" "PassiveFeature_Mobile_CounterAttackOfOpportunity"
data "PriorityOrder" "1"
data "Properties" "Highlighted"
data "StatsFunctorContext" "OnAttack"
data "Conditions" "IsMeleeAttack() and Character()"
data "StatsFunctors" "ApplyStatus(SELF,MOBILE_NO_AOO_SOURCE,100,1);ApplyStatus(MOBILE_NO_AOO,100,1)"

new entry "Mobile_DashAcrossDifficultTerrain"
type "PassiveData"
data "DisplayName" "Shared_Passive_Mobile_DashAcrossDifficultTerrain_DisplayName"
data "Description" "Shared_Passive_Mobile_DashAcrossDifficultTerrain_Description"
data "Icon" "PassiveFeature_Mobile_DashAcrossDifficultTerrain"
data "PriorityOrder" "1"
data "Properties" "Highlighted"

The later is referenced in a few status_boosts such as:

new entry "DASH"
type "StatusData"
data "StatusType" "BOOST"
data "DisplayName" "Shared_Status_BOOST_DASH_DisplayName"
data "Description" "Shared_Status_BOOST_DASH_Description"
data "Icon" "Action_Dash"
data "SoundVocalStart" "NONE"
data "SoundLoop" "Spell_Status_Dash_MO"
data "SoundStop" "Spell_Status_Dash_MO_Stop"
data "StackId" "DASH"
data "TickType" "EndTurn"
data "Boosts" "ActionResourceMultiplier(Movement,200,0);IF(HasPassive('Mobile_DashAcrossDifficultTerrain', context.Source)):StatusImmunity(DIFFICULT_TERRAIN);IF(HasPassive('Mobile_DashAcrossDifficultTerrain', context.Source)):StatusImmunity(DIFFICULT_TERRAIN_MUD);IF(HasPassive('Mobile_DashAcrossDifficultTerrain', context.Source)):StatusImmunity(DIFFICULT_TERRAIN_VINES)"
data "StatusPropertyFlags" "NonExtendable"
data "ApplyEffect" "c8db5bfe-06a2-4847-a496-bac8a11453ef"
data "StatusEffect" "30c73b0a-169a-46f9-9f6f-c3ea19117e38"

So whether the DASH status_boost is applied via a full action or BA it gives the same result.

For a melee character reaching the bad thing is of critical importance but you may have other options (fly, teleport etc)

Imo if you take the feat it's to avoid terrain effects