a) Fire based
beasts (i.e., Teras) are vulnerable to ICE flares - you will see
significantly more critical kills with an ice flaring weapon against a fire
based monster.
b) The opposite is true, too, of ICE based beasts, and FIRE flares.
c) An Ice flare followed by a Fire flare will CRACK (causing damage) STONE
based beasts.
d) STONE based beasts are vulnerable to EARTH flares, but you will not
necessarily see greater critical damage, as STONE beasts are naturally
padded with platemail equivalent armor.
e) Using a lightning flare against a Storm Griffin will charge its
"Lightning mote" maneuver attack (generally death to those in metal armors).
f) And I don't generally hunt Krolvin (EWave is annoying), but I suspect
they have been updated to reflect a natural padding versus ICE flares, and
therefore, may have a particular vulnerability towards FIRE flares.