The official GemStone IV encyclopedia.
The storm griffin is a magnificent beast, as if designed by the gods to embody fierce and graceful predation. Its front legs, forebody, wings, and head are those of a great eagle, complete with large powder-blue feathers and aquiline beak. The rear half of the creature's body is that of a powerful lion, with short, sandy blonde fur and a long feline tail. A tendril of electricity snakes across one outstreched claw as the storm griffin glares about with its piercing blue eyes.
Storm griffins, being a flying creature, are sometimes out of reach for melee attacks, predominantly when they have just soared into a room (though they also sometimes use it as a form of retreat).
Therefore, melee hunters should wait until the griffin itself attempts a melee attack (either with its beak or claws) against an adventurer before advancing (they can melee attack the yeti while remaining at high altitude). Ranged weapons and magical attacks perform as usual, although many knockdown and nature type spells (for example, Tremors (909)) do not affect them as they are not on the ground. They are also immune to stuns. When you see these birds Web (118) as soon as possible. These birds are even worse then the lesser griffins.
They also have various maneuver and spell style abilities which can cause roundtime, and can beat their wings for a Call Wind (912) style effect.
They can also release motes of essence, a maneuver attack which resembles the effects of Cone of Elements (518), and which affects both adventurers and creatures.
Storm griffins are immune to lightning flares and spells. However, they can be damaged by the standard damage caused by lightning flare weapons.
When using its Claw attack, the storm griffin attacks with two claws at once (similar to Two Weapon Combat).
The storm griffin feathers will give lightning flares to arrows when fletching.