The idea that there should be a spell called "Beastial Inheritance" came into my head as I woke up this morning but my sorta still asleep brain didn't have time to figure out what the spell does. Upon further reflection here's how I think it might work:
Magic-User Level 4
The MU must ritualistically kill a lycanthrope with a cursed blade then sheath it or put it away. If the next time the blade is used it is used to ritualistically cut a normal animal and a human then the bodies and spirits of the animal and the human are combined into a new were creature. The victim/volunteer need not be willing, and the Magic-User may cast the spell on him/herself. The creature will serve the Magic-User for the caster's level+2d6 days.
This spell gives the PCs the power to create whatever were-creature they want: were-sharks, were-chihuahuas, were-emus... That sounds like fun, right? Note the spell says "normal animal" so no were-tarasques or were-dragons.
That was fun. Here are a few more vaguely Halloween themed spells:
Magic-User Level 3
As the Magic-User casts this spell they undergo a ghastly transformation into an undead creature. The player may choose one die/table on the Undead Remix tables each round if a save vs. magic/Cosmic Doom/Necrotic Transformation is made. If the save is failed then roll the appropriate die and record the result. Once a save has been failed the remaining die are rolled normally. The spell's duration is the caster's level+d6 hours. At the end of the spells duration the caster must make another saving throw. If this is failed the undead state continues for another d6 hours after which another saving throw is rolled. If that roll fails the caster forever remains undead.
Magic-User Level 2
The material component for this spell is a bit of clay mixed with at least one drop of lycanthrope blood. The spell must be cast just as the moon is rising and must be completed before the moon clears the horizon. While the spell is being cast the clay is molded by the Magic-User into the form of a creature. at the spells completion the clay will grow in size to the equivalent of a number of normal men equal to the caster's level. The creature will come alive and serve the Magic-User until the moon sets. The creature will have armor class as chain mail and will have the same HD as the caster. The creature may have spikes or claws or wings or anything else that can be reasonably modeled in clay in a few minutes and they will be fully functional.
The DM should give the Player a ball of clay to mold to determine the nature of the Were-Golem that is created. A timer of 2 minutes should be used to limit the time that the creature can be formed.
Moon Ray Cartography
Magic-User Level 1
This spell must be cast on the night of a full moon. A clear crystal worth at least 100 gp must be held aloft so that a moon beam may shine through it. The light of the moon beam will form a map on the ground below the crystal. This map will describe clues to the nature and location of a treasure. Because the map will only last the caster's level+D4 rounds this spell is often cast over a bed of sand or unfurled roll of parchment to record the map.