Acid Splash 1e FAQ FAQ
Does Acid Splash require an attack roll in AD&D 1e?
No. The D&D Portal 1e conversion does not use an attack roll. The caster selects one creature within the 1-inch range; after any applicable magic resistance is resolved, the target makes a saving throw vs. spell. A failed save causes 1 point of acid damage and a successful save negates it. Armor Class, weapon attack matrices, and normal missile attack modifiers therefore do not determine whether the cantrip deals damage.
Later versions of Acid Splash sometimes use attack-roll mechanics, while other editions use saving throws. The Portal conversion deliberately chooses the saving-throw approach because it fits the minor person-affecting cantrip framework cleanly and avoids turning the cantrip into a weapon-like missile attack. That means the target's defenses are resolved through magic resistance and a save vs. spell rather than through Armor Class.
The caster does not roll to hit
Casting Acid 
D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash does not call for a weapon attack, missile attack, or separate spell attack roll. The caster only needs a legal creature within the spell's range.
There is therefore no attack result to compare against the target's armor class 
D&D Portal - Armor Class Combat rule Armor Class is a combat rule used by attacks,
damage, defenses, or turn order. Full link: https://dnd-portal.com/rules/combat/armor-class/. A heavily armored creature and an unarmored creature can have very different AC values without those values directly changing Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash's resolution.
The cantrip should not be treated as Melf's Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Arrow with smaller damage. That higher-level Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ spell has its own projectile procedure, while Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash uses a simpler save-based mechanic.
The target makes a saving throw vs. spell
If magic resistance does not stop Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash, the targeted creature makes a saving throw 
D&D Portal - Saving Throw D20 test rule Saving Throw is a d20 test rule used to resolve
uncertain outcomes during play. Full link: https://dnd-portal.com/rules/d20-tests/saving-throw/ vs. spell. That roll determines whether the minor burst of Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ causes hit-point damage.
A successful save negates the damage completely. A failed save causes exactly 1 point of Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/.
There is no half-damage outcome. The cantrip is intentionally binary because its total damage is already extremely small.
Armor Class does not resolve Acid Splash
Because Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash does not make an attack roll, descending armor class D&D Portal - Armor Class Combat rule Armor Class is a combat rule used by attacks,
damage, defenses, or turn order. Full link: https://dnd-portal.com/rules/combat/armor-class/ does not determine whether the spell succeeds. The cantrip bypasses the ordinary weapon-versus-AC resolution step entirely.
Likewise, adjustments that modify normal missile attacks do not automatically modify Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash. The spell is resolved as magic, not as a thrown flask, dart, arrow, or other projectile weapon.
A specific rule that alters saving throw D&D Portal - Saving Throw D20 test rule Saving Throw is a d20 test rule used to resolve
uncertain outcomes during play. Full link: https://dnd-portal.com/rules/d20-tests/saving-throw/, blocks magic, grants immunity, or provides magic resistance can still matter because those mechanics interact with the actual resolution used by the cantrip.
Why the Portal conversion uses a saving throw
The save-based design keeps the spell simple enough for 0-level apprentice magic. It avoids adding a projectile attack procedure, scatter rules, or a second resolution step to a cantrip that deals only 1 point of damage.
Official person-affecting cantrips provide precedent for living targets receiving saves vs. spell. D&D Portal follows that general design language while adding the original 1-point damage mechanic.
The saving throw D&D Portal - Saving Throw D20 test rule Saving Throw is a d20 test rule used to resolve
uncertain outcomes during play. Full link: https://dnd-portal.com/rules/d20-tests/saving-throw/ is therefore part of the homebrew conversion design. It should not be cited as evidence that an official 1e Acid D&D Portal - Acid Damage type Acid is a damage type used by attacks,
spells, class features, resistance, immunity, and vulnerability. Full link: https://dnd-portal.com/rules/damage-types/acid/ Splash spell used the same procedure.