are unique drops depth based?

[Sky]

if i kill a low level unique, say, Ulfast, either at DL20 or at DL70, will the quality of drops be higher at the lower depth ? Is there an incentive to avoid uniques until later on ?

[Estie]

Yes and yes.

[Philip]

As far as I know, unique drops are handled like any other drop, except most uniques have the DROP_GOOD or DROP_GREAT tag which messes with generation a bit. The short version is that if you kill a unique at depth, you get a guaranteed good object at that depth, while if you kill it deeper, you get a guaranteed good object at the average of your depth and the native depth of the unique. In theory, that is an incentive to avoid uniques until later on. In practice, the value of a guaranteed good object at current depth early is generally much higher than the value of a guaranteed good object at a couple dozen levels shallower than current depth later in the game.

IIRC an exception is O, in which unique drops, like any other monster drops, have a high chance of being replaced by gold when killed significantly deeper than native depth.

EDIT: Of course, the strongest incentive to avoid uniques until later is that early on there may be a cost to fighting uniques at depth, while later that unique will be free. Also, uniques with escorts are more or less always worth saving because it's an extra chance to get a whole escort of free objects. This silly behavior is why I love the O solution a lot.
The reason the value is higher early is that early on, good weapon, launcher, or ammo is probably worth using. You have a decent chance of getting one. Later on, it is rare for even egos generated at several dozen levels shallower than floor depth to be usable in most of your slots.

[Pete Mack]

The answer is "up to a point" How useful is a single DL 50 'good' drop at DL 90? What are the odds of it being good at DL 9? And what are the odds you will even see the monster that deep? Waiting a few extra levels to kill Wormtongue is perhaps a good idea, until certain useful items are likely to be present. But killing Bullroarer at DL 5 is likely to give an immediate and large increase in power.

[Derakon]

As I recall, the formula is that the item drop level is the monster's native depth, or the average of the current depth and the monster's native depth, whichever is larger. I don't believe this changes when the monster is unique, though I think their native depth is treated as being higher than where they actually show up (e.g. a dlvl-20 unique might drop items as if they were native to, say, dlvl 30). Don't quote me on that though.

[Nick]

Here is the calculation:

    /* Give added bonus for unique monsters */
    monlevel = mon->race->level;
    if (rf_has(mon->race->flags, RF_UNIQUE)) {
        monlevel = MIN(monlevel + 15, monlevel * 2);
        extra_roll = true;
    }

	/* Take the best of (average of monster level and current depth)
	   and (monster level) - to reward fighting OOD monsters */
	level = MAX((monlevel + player->depth) / 2, monlevel);

So unique drops are specifically boosted (doubled, up to a maximum of 15 levels boost), and then the drop is calculated based on (as Derakon says) monster level or average of current level and monster native level, whichever is better.

So Ulfast is level 16, that will be boosted to 31, and fighting him at DL20 will drop DL31 loot, at DL70 will drop DL50 loot. As Pete says, fighting him earlier is more likely to be useful.

[Sky]

i take it that the +15 is fixed for all uniques?

[Nick]

i take it that the +15 is fixed for all uniques?

It's double or +15, whichever is less - so Bullroarer, who is DL5, will drop DL10 gear (adjusted for what level you kill him on).

[DavidMedley]

I tried saving weak uniques so that the summon uniques spell would suck, in addition to getting better drops later, but I didn't find it worthwhile. I think you should kill any unique as soon as you can without risking death or burning boss fight consumables (which may be never).

[quarague]

The way angband is designed, delayed gratification is almost always a bad strategy. So while killing a unique you could kill now a few dungeon levels later will give you better loot in an absolute sense, the relative value of it to you will be smaller. That happens because player power increases faster than the drop quality increases for a fixed unique. So kill them as early as you savely can.

[Thraalbee]

But how about monsters generated in vaults? To me it seems that if I don't kill the early unique's, they are likely to turn up in the first couple of vaults.
If they are dead already typically something worse is there instead. Not sure if this is observation error or not.

[wobbly]

Vault monsters are picked the same way as any monster (with exact same routine) just usually with a boosted depth. If it's placing a depth + 5 monster it's just as likely to be a unique as if you were 5 levels deeper. Under depth uniques are even less likely in the vault then on the level as they are even more under depth, though they can end up there just by sheer quantity of vault monsters.