Does one of the two squares adjacent to the naga have an ignored item ('K' in the original keyset or 'O' in the rogue-like keyset would toggle the ignore setting and reveal those items)? For how many of the failed attempts was the other naga in the square adjacent to the naga?

If both grids were available and the cap on the number of monsters on the level hasn't been reached, the probability of the monster cloning with one wand activation is 1 - (7/9)^18 or 98.9%. If only one grid is available and the cap on the number of monster on the level hasn't been reached, the probability of the wand activation cloning the monster is 1 - (8/9)^18 or 88.0%. With the former, getting one clone in four attempts is highly improbable (.00051% chance of happening). With the latter, it's a bit more believable though still unlikely (.61% chance of happening). Without more information, I would say the code is working as expected (I would guess one of those other factors is coming into play for one or more of the attempts).

Could the code be better? Likely yes, though the current implementation has an advantage of being very simple; something that would work more reliably and more efficiently would be somewhat more complicated.

You can see in the messages the wand activation is working, the naga looks even faster. Just a moment prior, I pegged her buddy further back with the same wand. The guardian naga spawns! I then had 4 attempts in-a-row fail, while the newly spawned naga flew towards me at super-sonic speeds. And, I presume there are only 8 squares, max, for a new mob to spawn on around an existing mob. So, I calculate that to be 2 of 8 squares (hallway spots) for new nagas to spawn into. I think the code is not attempting to place new mobs with the same effectiveness as the 3.x code is/was/does/did.

I don't know how else to explain 4 failed attempts in a fairly empty hallway. No, no extra ignored-items in the hallway.

Did some testing in wizard mode and its working fairly consistently for me.

I'll keep watch over this peculiarity, see if I can pin it down further.

Yeah I have to say I'm not a great fan of this new flag--seems overly complicated and hard to understand. Seems like it was a feature mainly needed to balance rogues properly. Obv movement speed for rogues is a big deal. And probably also rangers that can back up firing Parthian shots at monsters way better with +1 movement. Well I guess and mages too. So it's really good for rogues and range attackers, not so much melee artists.

Using standarts Ive only found one item with movement speed: Boots of wormtongue. I pretty much didnt use them, but left it sitting in my home, thinking at the end game I might find them useful, but then even after I found 2x +15 speed rings, I still felt maxing out speed is best: its very nice to have 4.1 speed when facing a speed 3.0 or especially 3.8 monster (like wiruin)--the last bits of regular speed are a big deal.

Are there other items that have Movement speed flag that might be better than womtongue?

I find it amazing on melee characters. You can close distance in 1/steps the time. :) I think I had something crazy with a druid (pre nukes still melee) once like +5, all other mobs looked to be frozen in time when I was moving. XD

IIRC it was introduced for druid shapechanges, and then added to the odd item.

Any standarts other than Wormtongue?

Also regarding the prior post--well +5 is ridiculous--obviously that is something I would use LOL.

No, that's it. Of course with randarts, all bets are off :)

"Normal speed" should probably rather be called something like action speed, as opposed to movement speed, which is a modification of action speed for one particular type of action (movement).