Racial Stealth Modifier

Every race has a racial stealth modifier associated with it. From the in-game help for Racial Stealth:

Stealth is two-fold: A stealthy race is less likely to be attacked by aggressive mobs when a less-stealthy target also presents itself.

A stealthy race will also succeed more often with rogue skills such as blackjack, backstab and sneak attack.

Some examples of stealthy races include Drow, Halfling and Demonseed.

Some examples of non-stealthy races include Giant, Troglodyte and Troll.

Because we can't be sure exactly what the number is, we have simply assigned each race a rating of -3 to 2, with negative numbers being a penalty, 0 meaning "no modifier", and 2 being the best modifier possible. -3 is a failure rate of approximately 50%, -2 is 20%, and -1 is 5%. Note that size and groupsize both affect the success rate of disengage and slip, and are separate from the inherent stealth modifier.

There is also a separate archery damage modifier and melee damage modifier for each race.

Please note that all of this information has been gleaned from race pages here as well as discussion in-game, and is subject to change at any time. Also, entries for evolution races should reflect their maximum (highest evolve).

Legend
Great	2
Good	1
Average	0
Below Average	-1
Bad	-2
Terrible	-3

Creatable Races Stealth Modifiers

Race	Size	Racial Stealth Modifier
Centaur	L	-1
Deep Gnome	S	0
Draconian	M	0
Drow	M	0
Duergar	S	0
Dwarf	S	0
Elf	M	0
Ent	vL	-2
Firedrake	vS-vL	-3
Gargoyle	M	0
Giant	vL	-1
Gnome	S	0
Goblin	S	0
Halfling	S	1
Half-Elf	M	0
Half-Orc	M	0
Harpy	M	1
Human	M	0
Imp	vS-vL	-2 to 1
Kobold	S	-1
Kzinti	M	1
Lizardmen	M	0
Ogres	L	-1
Orc	M	-1
Troglodyte	M	-2

Remort Races Stealth Modifiers

Race	Size	Racial Stealth Modifier
Demonseed	S	2
Dragon	vL	-2
Golem	L	-2
Griffon	L	0
High Elf	M	0
Hobgoblin	S	1
Minotaur	L	-2
Miraar	M	0
Sprite	vS	0
Troll	L	-1
Tuataur	M	2

Stealth Modifiers, Rogue Skills, And You

Performance as a rogue is not exclusively or even primarily determined by the stealth modifier. Dexterity, intelligence, racial damage modifier and size also affect rogue skills to varying degrees but these are separate from the hidden natural stealth modifier as described above. Many players strongly prefer sturdy races with high damage output to small agile races when they create a rogue, as rogues have difficulty avoiding taking damage in the course of their duties.

Most races do not have an inherent stealth modifier. While poor aptitude to stealth is obvious (your skills fail to work), talent at stealth only becomes a major factor at Lord, when rogues obtain slip and disengage: both of these skills are very demanding on a rogue's sneaking ability. Most races which are considered "stealthy" are just neutral at stealth with above average intelligence/dex, which is sufficient to successfully backstab all the time, but does not enhance slip/disengage performance, as both of these skills rely more on racial size and racial stealth. There is a further complicating factor, which is overall group size: the larger the crowd, the higher the likelihood of sneaking off. Large races such as troll and pain elemental are more sensitive to changes in groupsize. From this we can see differences in orc and troll stealth performance, despite them having the same negative modifier in theory - orcs have more dex, and also are medium instead of large, so they stab slightly better and slip significantly better.

"Nils" on assassinate and backstab occur at a flat rate regardless of race or class.