Immunity to poison makes her a great front-liner in the first few levels, when you have to deal with poison a lot from all those nasty spiders in the Old Sycamore etc. Plus the fact that she can't die helps sometimes, too. Jaethal is a lot more reliable on that department. In other runs I was ripping out my hair when my frontline suddenly crumbled from Valerie getting feared or otherwise CCed. Front-liners need to be able to take a lot of punishment, and all those sweet immunities she gets from being undead help a lot. What I really liked about Tank Jaethal is the fact that she is Undead. I didn't really go the whole persuasion/dazzling display stuff with her, which seems to be the popular thing to do with any tanks. Just activate her defensive Judgements on tough fights, hand her a shield and any good one-hander. True, her AC may not be quite as high as that of Valerie, but I was playing on Challenging and it was more than enough for that.

I build Jaethal into a tank in my Lawful Evil run and I had a ton of fun with it. Trip line is also a good option to go but i go dreadful carnage on her as she will crit often and kill often with Serpent Prince. Jaethal 1 level fighter dip, exotic weapon proficiency fauchard. Thats a tank for you who can deal damage because Magus Scion can. Gets wings, +6 Natural armor from bloodline + dd, wears heavy armor, 3 mobility + crane feats adds another 8ish armor in melee and can cast mirror image/displacement/haste/greater invis. Dip in to DD at 8 for 4 levels then carry on magus. Grab him crane style/wing/riposte by getting dodge and improve unarmed strike. Regongar becomes a strong tank after level 7. He will never be super effective in melee but he can debuff really well and add more value then crossbow tristian who is only good at buffing and healing. I like to split 3/3 melee/range so makes it more ideal for me anyways. Extra channel here and there, thats gonna make him quite good and that way you can have a melee cleric and get a secondary caster if you want. Around level 10 the loots(mallet of woe / protector of unjust / crusader plate) will make him well equipped for melee and get a few spell foci necro on him and he will be quite strong. Keep going cleric with him and get some offensive teamwork feats (outflank, precise strike). Harrim gets quite good later on in the game when his spell lists have more variety.

Pathfinder kingmaker jaethal build