Not to worry; the boneshard skeleton's Boneshard Burst is not an immediate action. It has no listed action, but since it can trigger at 0 hp or less, it would have to be "no action," if anything were specified.
-Dan'L
Boneshard Troll Skeleton Level 11 Brute
Medium natural animate (undead) XP 600
HP 137; Bloodied 69
AC 23; Fortitude 22; Reflex 22; Will 21
Speed 6
Immune disease, poison; Resist 10 necrotic; Vulnerability 5 radiant
Initiative +8
Perception +7
Darkvision
Standard Actions
m Scimitar (necrotic, weapon) • At-Will
Attack: +15 vs. AC
Hit: 2d8 + 6 damage (crit 2d8 + 22)plus 10 necrotic damage. If the troll skeleton takes acid or fire damage, it does not deal necrotic damage with this attack until the end of its next turn.
m Boneshard (necrotic) • At-Will
Attack: +15 vs. AC
Hit: 1d6 + 6 damage, and ongoing 5 necrotic damage (save ends).
Triggered Actions
C Boneshard Burst (necrotic)
Trigger: When first bloodied and again when the boneshard skeleton is reduced to 0 hit points.
Attack (Immediate Reaction): Close burst 3; +14 vs. Reflex
Hit: 2d6 + 6 necrotic damage.
Str 16 (+8) Dex 16 (+8) Wis 14 (+7)
Con 17 (+8) Int 3 (+1) Cha 3 (+1)
Alignment unaligned
Languages —
Equipment scimitar
Monster found in P1 King of the Trollhaunt Warrens and Compendium
© 2010 Wizards of the Coast LLC, a subsidiary of Hasbro, Inc. All rights reserved. This formatted statistics block has been generated using the D&D Adventure Tools.
It's not in P1 but it is in the Monster Builder.