Okay, here's that Assassin. He's really a nasty little bastard. Using the Alternate Tiefling stuff to replace his Darkness ability with Small Size.
His basic tactic is to sneak up on his target (possibly under Invisibility), use his Silent Greater Invisibility, and then go to town with Silent Scorching Ray spells and Tricky Spelled Quickened Scorching Rays.
That's 6 attacks each at +16 to hit touch AC each for 9d6 damage of whatever element he likes. The vast majority of foes will take around 189 damage. That's really awful.
His tactics will continue in this vein as necessary to kill his target or targets (though he's more than smart enough to know he lacks the spells to take a whole PC group).
Defensively, he's a bit weak for his CR, but he can use spells to bolster it, and I think his offense makes up for it, don't you?
He is always under the effects of Mage Armor, and Contingency. Just in case. He'll flee with the latter if things aren't going his way starting on around the end of the third round (the first two rounds his Swift Actions are used with Scorching Ray).
He has whatever spells in his spellbook for use with his Bonded Object that the GM decides he has.
CR 15
Tiefling Wizard (Evoker-Admixture) Wizard 5/Assassin 4/Arcane Trickster 7
NE Small Humanoid
Init +8; Senses Perception +20, Darkvision 60 ft.DEFENSE
AC 30, touch 20, flat-footed 25 (+4 Armor, +4 Dex, +3 Deflection, +2 Natural Armor, +4 Shield, +1 Size, +1 Insight, +1 Dodge)
HP 115 (12d6+4d8+53) + False Life
Fort +11, Ref +14, Will +13 (+2 vs. poison)
Resist cold 5, electricity 5, fire 5,OFFENSE
Spd 30 ft.
Melee dagger +14/+9 (1d3/19-20)
Ranged longbow +14/+9 (1d6/x3) or touch attack +14
Special sneak attack +5d6SPELLS (CL 12)
6th: Quickened Scorching Ray, Quickened Scorching Ray, Getaway,
5th: Silent Greater Invisibility, Magic Jar (DC 22), Polymorph, Teleport, Wall of Force,
4th: Greater Invisibility, Greater Invisibility, Dimension Door, Silent Haste, Resilient Sphere,
3rd:...
Great !!! thank you !!!
I wish to use it for my home campaign, the PC's group has made some recurring enemies, powerfull enough to pay for the services of the tiefling. PC's average level 14 and they are smart enough to be a challenge the tiefling can't refuse if given the right payment