This spell has been adapted from a spell of the same name in Dragon Magazine issue 343.

Spider hand

1st level Transmutation

Casting Time: 1 action
V, S (Caster’s own hand)
Concentration, up to 1 minute

You harmlessly detach your hand, which deforms into a small, monstrous spider (See monster manual page 337) that you control. Roll initiative for the spider separately to the caster, and control its actions on its own turn. You can see through the spider’s eyes and it can travel 120 feet away from you. If the hand-spider is killed or prevented from returning to you, your hand is restored when the spell ends, but you take 1D6 points of psychic damage. If you command the spider to return to your hand, it harmlessly reforms on to your arm, ending the spell.