Bind storm to ship [822]
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Usage: BIND <storm>
Required aura: three or more points
Time to cast: seven days
Bind an existing storm to a ship. The caster must be the owner of
the storm (having summoned it himself, or seized control of it),
and must be on the ship the storm is to be bound to.
Subsequent movement of the ship will cause the storm to follow.
This can be especially useful if a wind storm is bound to a
roundship, as the roundship will enjoy faster travel while the
aura of the wind storm lasts.
The required aura is 3 or more points, but it does not list the varialble for
the aura in the description as it does in other spells (i.e. skill 809 or skill
825)
My question: what is the required aura for this spell?