The creature entry is right below its civ entry
In any case, it's here. I used the HUMANOID_SIMPLE body for the creature.
[CREATURE:ANCIENT]
[NAME:ancient:ancients:ancient]
[TILE:'A'][COLOR:255:255:255]
[FIREIMMUNE][FIREIMMUNE_SUPER]
[BODY:HUMANOID_SIMPLE:MOUTH:HUMANOID_JOINTS:4FINGERS:4TOES:2EYES:HEAD_HORN]
[BODYGLOSS:CLAW_HAND]
[PREFSTRING:warm hearts]
[BODYGLOSS:TALON_FOOT]
[BODYGLOSS:CLAW_HAND]
[BENIGN]
[EQUIPS]
[CRAFTSMAN_NAME:shaper:shapers]
[HAMMERMAN_NAME:ancient of the Hammer:ancients of the Hammer]
[SPEARMAN_NAME:ancient of the Spear:ancients of the Spear]
[CROSSBOWMAN_NAME:ancient of the Bolt:ancients of the Bolt]
[AXEMAN_NAME:ancient of the Axe:ancients of the Axe]
[SWORDSMAN_NAME:ancient of the Blade:ancients of the Blade]
[MACEMAN_NAME:ancient of the Mace:ancients of the Mace]
[PIKEMAN_NAME:ancient of the Pike:ancients of the Pike]
[BOWMAN_NAME:ancient of the Arrow:ancients of the Arrow]
[SPEECH:dwarf.txt]
[NOPAIN][EXTRAVISION][NOBREATHE][NOBLEED][NOSTUN][NONAUSEA]
[NOSTUCKINS][NOSKULL][NOSKIN][NOBONES][NOMEAT][NOEXERT]
[DAMBLOCK:15]
[NOFEAR]
[NOSMELLYROT]
[SIZE:14]
[ATTACK:MAIN:BYTYPE:GRASP:raises its hands above its head, then crush:raises its hand above its head, then crushes:3:9:BLUDGEON][ATTACKFLAG_WITH]
[ATTACK:MAIN:BYTYPE:UPPERBODY:bodyslam:bodyslams:2:12:BLUDGEON][ATTACKFLAG_WITH]
[ATTACK:MAIN:BYTOKEN:4FINGERS:grip with a frightening strength:grips with a frightening strength:2:8:PIERCE][ATTACKFLAG_WITH][ATTACKFLAG_CANLATCH]
[ATTACK:SECOND:BYTOKEN:HEAD_HORN:lumber forward and impale:lumbers forward and impales:1:9:GORE][ATTACKFLAG_WITH]
[SWIMS_LEARNED][SWIM_SPEED:1500]
[INTELLIGENT]
[CHILD:12][CHILDNAME:youngling:younglings]
[BIOME:ANY_LAND]
[MAXAGE:3000:3500]
[NO_DRINK][NO_EAT][NO_SLEEP]
[PERSONALITY:IMMODERATION:0:20:30]
[PERSONALITY:VULNERABILITY:0:10:10]
[PERSONALITY:STRAIGHTFORWARDNESS:0:85:100]
[PERSONALITY:ALTRUISM:100:100:100]
[PERSONALITY:CHEERFULNESS:100:100:100]
[PERSONALITY:INTELLECTUAL_CURIOSITY:80:90:100]
[PERSONALITY:GREGARIOUSNESS:20:60:100]
[PERSONALITY:ACTIVITY_LEVEL:100:100:100]
[PERSONALITY:DUTIFULNESS:100:100:100]
[PERSONALITY:COOPERATION:80:90:100]
[PERSONALITY:ANGER:0:0:0]
[PERSONALITY:SELF_DISCIPLINE:100:100:100]
[PERSONALITY:ORDERLINESS:100:100:100]
[PERSONALITY:ACHIEVEMENT_STRIVING:100:100:100]
[LAYERING:200]
[MATERIAL:METAL:STEEL]
[GRASSTRAMPLE:0]