Year of the Demon Lord - The Crimson Bone Dagger

Image Source: http://darkelements.us/bone.htm

This was partially created ad hoc during my group's play of Survival of the Fittest, and then fully planned afterwards as a way to roll out some enchanted items into the game. The PCs didn't know all of the dagger's capabilities at first, and only discovered them as appropriate based on play.

 Crimson Bone Dagger 

• Necromancy implement (can be used to discover the tradition).
• Grants a +1 to all spell checks for Necromancy spells.
• Lifestealer: Your recovery rate is reduced by 1. So long as it has "fed" on at least one recovery the dagger is preternaturally sharp and deals 1d6 damage instead of the usual 1d3 damage. This lasts until after you complete a rest. 
• Dominator: After a successful attack on an undead creature the wielder may make a Will attack (with +1 from this weapon) against the will of the undead. On a success the undead becomes compelled for 1 min. Boons or Banes may apply at the GM's discretion.
• Alternately when attacking an Animated corpse in this way the caster may elect to use a triggered action to expend a casting of Animate Corpse. If they do so the target becomes compelled permanently and automatically.
• Antagonizer: Spirits attacked by the blade become filled with rage and manifest as phantoms, or possibly even wraiths.