Uniques cannot be killed with a poison needle, except for the babble at the bottom of the Arena, who's a hardcoded exception.

What is the go with a poison needle? I've never tried one.

Most of the time it deals exactly one point of damage, but occasionally (think around one in ten times) it will deal (monster's HP + 1) damage, which will instakill the monster.

The chance in code (from 7.1.Salmiak) is randint1(randint1(r_ptr->level/7)+5) == 1
This means that 1-time-in (random number from 6 to (5+monster level /7) ) it will kill the mob.
So for the Metal Babble guardian in the Arena, a level 80 mob, you would have 1-in-6 (best case) to 1-in-16 (worst case) chance to instantly kill it. I think (Statistics class was a long time ago) the average chance is 1-in-11.

But it varies a little based on monster level, so for instance a level 50 mob would range from 1-in-6 to 1-in-12 (average 1-in-9), while for a level 100 mob the max is 1-in-19 (average 1-in-13).

1 in ~8.5 for DL 50 monster. (You can't add denominators.) For what it's worth, the odds are of order 1/log(DL).

Bug/RFE: Giants, etc. & Kronos' Sickle
 

Titans have Kronos as their racial boss, yet his sickle is, unflavorfully, not suitable for Giant wielding.

Posted for Rolanako.

Bug(?): Death-Swords and Disenchantment
 

The function for Death-Swords getting disenchanted and losing their essences (r_sword.c, line 1114) doesn't appear to be called anywhere; as far as Rolanako and I can tell Disenchantment isn't any more dangerous or annoying for Death-Swords than any other character, even though I could have sworn that was not the case at some point.

Note that since the babble doesn't levitate, etc., it has to spend extra energy to enter trees. It will fireball trees if you're next to them, but you can often stand one square away and approach just after it enters them without making it blink. Of course you'll need a good pile of ?Forest Creation for this, or to have some other means of tree creation.

So I've gone back to coffee break, if I'm going to die around CL30 may as well get there quicker.
But how do you guys control the pacing? Do you just sit and rest in DLs you've pretty much cleared waiting for monsters and loot to respawn? Or do good players not really need to pace it?
I rarely get to CL35, and find that it's too much for me id DL is > CL+5. And when under CL25 I keep DL < CL

Mainly I avoid killing summoners unless I dont need more xp at the time

Bug?: Devicemasters and Transfer Essence
 

The Transfer Essence ability for Devicemasters (devicemaster.c, line 265) seems to only let you transfer from deeper objects to ones of shallower depth, yet its safety check message (line 290) makes it seem like it's supposed to work in the opposite way (from shallow objects to ones of deeper depth).