I'm working on adjusting a monster to fit the next adventure I run, but I'm not entirely certain what its CR will be. I started with a CR 10 monster, changed its attack, upped its HP and gave it a new ability(basically an SLA as an extraordinary ability).
LUNA MOTH CR 12?
XP 9,600
N Huge vermin
Init +6; Senses darkvision 60 ft., tremorsense 60 ft.; Perception +0
DEFENSE
AC 23, touch 10, flat-footed 21 (+2 Dex, +13 natural, –2 size)
hp 176 (16d8+48)
Fort +13; Ref +7; Will +5
Immune vermin traits
OFFENSE
Speed 20 ft., fly 60 ft. (good)
Ranged 2 Moonbeams +12 Ranged Touch (2d12)
Space 15 ft.; Reach 10 ft.
Special Attacks drone; Lunatic Scream(DC 17)
STATISTICS
Str 20, Dex 15, Con 16, Int --, Wis 11, Cha 2
Base Atk +12; CMB +19; CMD 27
Feats Improved Initiative
SPECIAL ABILITIES
Drone (Ex)
The rapid beating of the helix moth’s wings creates a droning sound that is audible up to 60 feet away. This droning clouds the minds of all creatures within 30 feet that hear it except other helix moths. A successful DC 21 Will save negates the effect. The save DC is Constitution-based.
On a failed save, a creature suffers a -4 circumstance penalty to attack rolls, checks and saves for 1 minute. After this time, a new save can be attempted (same DC) if the helix moth’s droning can still be heard and the creature is within range. If this save fails, the creature remains affected for another one minute. This continues every minute until a successful save is made or the combat ends. A creature that makes a successful Will save is unaffected by the droning of that helix moth for one day. The droning is a free action so long as the helix moth is airborne. On the ground, it may beat its wings as a move action with the effects as above.
Lunatic Scream (Ex)
Once every 1d4 rounds, the Luna moth can beat its wings much faster, increasing the drone from a low frequency infrasound to a high pitched shriek, affecting foes within 60 feet. It deafens and damages creatures in its path. Any creature within the area is deafened for 1 round and takes 5d6 points of sonic damage. A successful save negates the deafness and reduces the damage by half. Any exposed brittle or crystalline object or crystalline creature takes 1d6 points of sonic damage per caster level (maximum 15d6). An affected creature is allowed a Fortitude save to reduce the damage by half, and a creature holding fragile objects can negate damage to them with a successful Reflex save. Lunatic Scream cannot penetrate a silence spell.
Moonbeam (Ex)
A Luna Moth can fire beams of moonlight to damage foes. These Moonbeams have a maximum range of 40 feet. This attack overcomes damage reduction of any type.
Its attacks are almost guaranteed hits(+12 on a ranged touch) though not necessarily all that high damage, its HP is high for that CR and it can basically cast Shout as an omnidirectional SLA once every 1d4 rounds(which effectively negates its drone ability by deafening those that fail the saves). The adventure it's going to appear in will be a split party adventure where it'll be a Summoner/Druid(11); Alchemist(9) and 2 Crossbow fighters(9) against this thing. So it's not like they'll lack for ranged power. I'm just curious as to what those of you familiar with this sort of thing feel would be an appropriate challenge rating for this thing.