Stinger

The subject sports a tail reminiscent of a scorpion’s, starting from his lower back and arcing overhead, the poisonous sting floating above him. Almost 9 feet in length and as wide as the character’s back at its base, the tail cannot be concealed under clothes; off-the-rack containment suits or other similar protective garments do not fit.
Type: Major positive.
Effect: The mutant’s tail is quick and agile. He may use it to attack and may combine it with other natural attacks to make a full attack action at his full base attack bonus. In addition, the character can make an extra attack of opportunity with the tail. When the tail hits, it inflicts 2d6 points of damage and delivers a poison (DC 10 + half character level + Constitution modifier; 1d2 ability damage, cure 2 consecutive saves). This poison targets Strength, Dexterity, or Constitution, determined randomly at the time of mutation or specified by the designer for biotech implants and grafts.
In addition to the combat advantages, the agile tail is also useful in other ways. It can make climbing certain surfaces or balancing on narrow spaces easier, and the character can use it to brace against an object. In instances where the GM feels that a tail may make life easier for the character, a +2 circumstance bonus is in order. However, due to its size, the tail also gives the mutant a -2 penalty on all Stealth attempts, and donning a disguise is nearly impossible. If the mutant also has the Prehensile Tail mutation, the stinger is retractable (a free action to retract or extend), allowing the mutant to manipulate things without stinging them.
The mutant’s poison can be extracted. The extraction requires a Craft {pharmaceuticals} check against DC 18; each successful extraction yields 1d3 doses. Each does harvested this way neutralizes the mutant’s ability to deliver poison (but not to use any of the tail’s other features) for 1 hour.
Biotech: Graft.