You raise to un-life a tiny creature that has been slain by yourself or a member of your party. The servant has the statistics of the original creature though it is classed as undead. Your servant retains the ability to interact with members of its own species and pass for one of them, but will be discovered as undead on a DC10 investigation check.
the creature retains the personality is had in life but will always obey you. Although it cannot attack it still rolls its own initiative in combat scenarios and is able to take other actions as normal.
When the creature drops to 0 HP it returns to being a dead corpse and cannot be remade into an undead servant again. you can only have one undead servant at a time, if you cast this spell on another corpse your previous undead reduces to 0HP.
* - (graveyard lichen, ash and the fresh corpse of a tiny creature killed by yourself or a party member)