Shadowtouched Alternate Advancement

The DMG presents standard rules for increasing a monster's level: basically, increase the monster's attack rolls and defenses by one for every level added, increase the damage dealt by the monster's attacks by one for every two levels added, and increase the monster's hit points for each level added by an amount depending on its role.

Alternate advancements are a variant approach to increasing a monster's level similar to 3e templates, in which some or all of the standard adjustments gained by a monster for adding a level are replaced by other abilities. The following is an example of an alternate advancement.

Shadowtouched

The shadowtouched alternate advancement may be used to create a creature that has been tainted by necrotic energy. Some may be natural creatures that were corrupted because they strayed into an area infused with dark power. Others have attained this status through the use of obscure rituals.

Shadowtouched
Level: +1
XP as its new level
Initiative +1 if its new level is even
Senses Perception +1 if its new level is even; darkvision
HP as its role and new level
Defenses +1 to its three highest defenses
Resist 5 necrotic; increase necrotic resistance to 10 if its new level is 11th or higher, and to 15 if its new level is 21st or higher

Powers
or Necrotic Smite (standard; encounter) * Necrotic
The shadowtouched creature makes a basic attack. If it hits, it deals additional necrotic damage equal to 5 + half its new level, and the target is weakened (save ends).
Bloodied Retaliation
The shadowtouched creature gains a +2 bonus to attack rolls against the creature that first bloodies it in an encounter.

Skills +1 if its new level is even
Ability Scores modifiers +1 if its new level is even

The shadowtouched alternate advancement does not change the base creature's origin. However, a successful Arcana check allows a character to recognize that a creature is shadowtouched, even if he is unable to identify the base creature, and to know the powers and resistances of the shadowtouched alternate advancement, as per the rules for monster knowledge checks.

The following is an example of a shadowtouched creature:

Shadowtouched Dire Rat, Level 2 Brute
Medium natural beast (XP 125)

Initiative +3
Senses Perception +6; darkvision
HP 48; Bloodied 24; see also bloodied retaliation
AC 16; Fortitude 16, Reflex 14, Will 11
Immune filth fever; Resist 5 necrotic
Speed 6, climb 3

Bite (standard; at-will) * Disease
+4 vs. AC; 1d6 + 2 damage, and the target contracts filth fever; see also bloodied retaliation
Necrotic Smite (standard; encounter) * Necrotic
The shadowtouched dire rat makes a bite attack. If it hits, it deals an additional 6 necrotic damage and the target is weakened (save ends).
Bloodied Retaliation
The shadowtouched dire rat gains a +2 bonus to attack rolls against the creature that first bloodies it in an encounter.

Alignment Unaligned
Languages –
Skills Stealth +8
Str 14 (+3) Dex 15 (+3) Wis 10 (+1)
Con 18 (+5) Int 3 (-3) Cha 6 (-1)