## When a user registers their mobile number during sign up, how can we verify that they really own the mobile number?

A lot of websites send a 4-digit or 6-digit one-time code to a mobile number via SMS or phone call when the user registers a mobile number on the website?

Is this a secure way to validate the ownership of mobile number? Are there any issues with it?

If it is not secure, are there any better alternatives?

## Can alchemists prepare alchemical items without reading their formula book?

The Pathfinder 2 alchemist class can prepare alchemical items if they have the item’s formula in their formula book. However, the class features never explicitly say that the alchemist needs to read the formula book, or have the formula book nearby, when crafting these items during their daily preparations.

You can use this feat to create alchemical items as long as you have the items’ formulas in your formula book.

… choose an alchemical item of your advanced alchemy level or lower that’s in your formula book …

You create a single alchemical item of your advanced alchemy level or lower that’s in your formula book…

The items you can select depend on your research field and must be in your formula book.

As a point of comparison, the wizard class explicitly requires that wizards must study their spellbook daily in order to prepare spells. So a wizard can’t feasibly go adventuring without it.

At 1st level, you can prepare up to two 1st-level spells and five cantrips each morning from the spells in your spellbook…

But the alchemist class has no such wording. Taken literally, this would mean that the alchemist can prepare items as long as (1) their formula book exists somewhere and (2) the item’s formula is written in the formula book. They could leave their 1-bulk formula book in a safe location and go adventuring without penalty.

In terms of rules-as-written, is this interpretation correct? Or do they need their formula book on hand during their daily preparations?

## Does a Wizard copying a spell count as one of their two new spells for a level?

In D&D 5E Wizards get an additional two spells per level to add to their spellbook:

Each time you gain a wizard level, you can add two wizard spells of your choice to your spellbook.

If a Wizard has a handful of Scrolls and another Wizard’s spellbook they have found while adventuring, can they attempt to scribe them all (assuming they are of the necessary spell level and have the time and money to do so), or are they limited to 2 new spells per level?

## Can a character dodge/fly if they use up all their speed?

There’s something about the language in the rules for Dodging and Flying that confuses me. In both cases, both can only performed so long as the character’s Speed is not ‘reduced to 0’.

By that logic, if a character with 30 feet speed, were to say use the full 30 feet speed on their turn, would that prevent them from taking the Dodge action?

Likewise, if a creature had, say, a Flying speed of 60 feet, would there character have to fly 55 ft in order to stay aloft or risk falling?

(As a side note, how do attacks like Thunderwave which force movement play into this? If a Thunderwave hits a 30 feet speed character who has only moved 25 feet, would that prevent the character from being able to use Dodge until their next turn?)

## Do you allow players to go against their alignment? 5e [closed]

How do you enforce alignment? Is there a roll for something like this? IE. my Lawful Good character needs to lie to a child in order to achieve X. I roll a D20 and add my wisdom modifier and need a 15-20.

I’m creating a character for 5e and only ever played 3.5. Want to play LG but don’t want to be too constrained.

## What happens when I redirect an attack with mounted combatant but I am outside the reach of their weapon on a grid?

The mounted combatant feat (PHB 168) allows someone to "force an attack targeted at your mount to target you instead."

Suppose I am playing on a grid. Let E be enemies without reach/ranged weapons. M be the spaces a large mount occupies. And R be the space I occupy while riding the mount.

$$\begin{array}{|l|l|r|} \hline \text{E} & \ \hline \text{E} & \text{M} & \text{R}\ \hline \text{E} & \text{M} & \text{M} \ \hline \end{array}$$

What happens when I redirect an attack with mounted combatant but I am outside the reach of their weapon on a grid?

## Finding $l$ subsets such that their intersection has less or equal than $k$ elements NP-complete or in P?

I have a set $$M$$, subsets $$L_1,…,L_m$$ and natural numbers $$k,l\leq m$$.

The problem is:

Are there l unique indices $$1\leq i_1,…,i_l\leq m$$, such that

$$\hspace{5cm}\left|\bigcap_{j=1}^{l} L_{i_{j}}\right| \leq k$$

Now my question is whether this problem is $$NP$$-complete or not. What irritates me is the two constraints $$l$$ and $$k$$ because the NP-complete problems that were conceptually close to it that I took a look on (set cover, vertex cover) only have one constraint respectively that also appears in this problem.

I then tried to write a polynomial time algorithm that looks at which of the sets $$L_1,…,L_m$$ share more than $$k$$ elements with other sets but even if all sets would share more than $$k$$ elements with other this wouldn’t mean that their intersection has more than $$k$$ elements…

This question kind of comes close but in it there is no restriction on the amount of subsets to use and the size of the intersection should be exactly $$k$$, but maybe this could be useful anyways.

Can somebody further enlighten me ?

## Can a changeling increase their Charisma by +3 at character creation?

In Eberron: Rising from the Last War, the changeling race says the following (p. 18):

Ability Score Improvement. Your Charisma score increases by 2. In addition, one ability score of your choice increases by 1.

Is there anything stopping you from choosing Charisma again for your additional +1? It seems a bit cheeky to me, since no other race can have a +3 at character creation, but on the other hand, the two sentences do seem to be rather deliberately disjointed. It’s not like the wording of the half-elf’s ability score improvement, as this Q&A explains, so does that mean that gaining a +3 to Charisma is a legitimate choice?

Obviously this is assuming that a DM doesn’t insist otherwise, and we are also assuming that this won’t allow an ability score to go above 20

## Does a creature under the effect of Motivational Speech still get advantage on their next attack if the spell ends for them?

The spell motivational speech (Acquisitions Incorporated, pg. 77) says:

For the duration, each affected creature gains 5 temporary hit points and has advantage on Wisdom saving throws. If an affected creature is hit by an attack, it has advantage on the next attack roll it makes. Once an affected creature loses the temporary hit points granted by this spell, the spell ends for that creature.

So when the effected creature is hit by an attack, the spell grants the creature advantage on their next attack. But getting hit by an attack is going to be accompanied by damage – and 5 points seems like it will very often be gone with a single attack.

Does a creature hit by an attack still get advantage on its next attack if that attack dealt 5 or more damage? Or does the spell end for them immediately and they do not get advantage on the next attack?

It just seems like this effect is going to be self-defeating a lot of the time – the thing that grants the advantage is the thing that takes it away. Am I missing something?

Note, temporary hitpoints are always lost first, so no holding on to them while subtracting damage from your standard hitpoint pool. Sorry Jim, it was a clever thought.

## Can the people who live in this maze get lost in their own maze in Tomb of Annihilation?

I hope the title isn’t so ambiguous such that it doesn’t actually resemble what I’m asking, but I’m trying to keep the title spoiler free.

So, in the Tomb of Annihilation adventure for D&D 5e, there is a location in Chult called Dungrunglung (pp. 49-52). This location includes a maze.

So, the moment the party step into the maze (which surrounds the grung settlement of Dungrunglung), the grungs "greet" them immediately and escort them to the centre, which of course means they are going through the maze with the party. On page 49, it has this to say about the maze itself, and what one may expect whilst trying to navigate it:

The maze’s passages are open to the sky and magically change configuration every minute or so, turning passageways into dead ends, and vice versa. Whichever character is leading the way through the maze must make six successful DC 15 Wisdom (Survival) checks to find the entrance to the settlement (area 2). Each successful or failed check represents 1 minute of searching the maze.

This, to me, implies that the grungs themselves can get lost in their own maze (and after apparently having just travelled through it already to greet the party). Is this true?

Is there anything that I’ve missed that might imply that, while being guided through the maze by the grungs, the (escorted) party and grungs do not get lost? Or do the party or the grungs still need to make Survival checks, potentially getting lost?