Baldur's Gate : The Sword Coast Chronicles : NWN2 Persistent World

Considering making a monk/warlock devil worshipper who turns into a devil via Word of Changing invocation. Would take fiendish heritage feats and everything nasty you can get your hands on, but honestly unsure how to make it happen. 11monk/16War/3..? Tips? How bad will this build me, all things considered? And what abilities should I focus on?

Problem is you cant cast, use feats, heal or throw epic spells in devil form, so once you transform you can only swing in melee. And you cant buff like a druid or wizard before you do so with your own magic. Most builds dip monk for WIS to AC bonus as this works. So yuo at least end up with good AC. But you dont use WIS in any other way then this bonus, ok you get a good WILL save but thats it. There are no changes to this invocation on our server.

http://nwn2.wikia.com/wiki/Word_of_Changing

Your only options are the modes available in the modal bar like IPA, HIPS, ICE, etc...
No items work in this form, so if you plan to fight al lthe time in this form then basically you can go nude into battle...
You could try getting some buffs from wands, others could be cast on you from party members. But its really a chore to do it every time, and becomes painfull quickly.

What do you GET from the build?

Well you can drop your physical abilities to 10 or lower, they are overwritten, hence you can get really high wisdom, intelligence or charisma. This transfers to AC, skill points and your warlock DC's and invocations like Dark Ones Own Luck.
You could dip Blackguard. Its a solid choice. You take PA and later IPA in the process and azquire Divine Shield and Divine Might. You can turn them on and then shift into the devil form.
You are immune to poison and fire, your wizard friends will ove you tanking for them, they can spam CLoudkill, Fire Walls, Incendiary Clouds at your feet. You are immune to such spells like fireball, always dangerous flame arrow, etc, etc.
You have SR 28, marginal, but usefull vs those low level mob casters.
You get DR10 to good or alchemical silver.
You get regeneration 5HP/round, which is great as you cant really heal in devil form.

Your AC will end around 50. Which is enough for most server mobs. You will need help with bosses.

Due to server changes feats that apply to unarmed fighting should apply to the devil form, hence a 4 lvl fighter dip is a great idea for weapon focus unarmed, weapon mastery unarmed, improved critical unarmed. And you need to take them as feats from items wont transfer so you cant count on those monk belts, gloves, rings, to give you those feats.

Your AB will probably be in the range 35 to 40. Which isnt ideal... But as a monk you could use Flurry of Blows to get more attacks on your high AB.

Also remeber to cast all your usefull warlock buffs before you shapeshift, they will transfer to your form.

Terrible idea at the momment.
50 ac and 35-40 AB like in a post above are possible without shape change.
No Gutual Invocations feat, no weapon dmg/stats transferred to a new form, you literally become weaker version for a price of invocation slot. Not fun at all - unless some dev confirms that changes are planned in a future I wouldn't take this route.

Personally i think it has 2 big problems that stop me from playing such character.

1. the DMG output in devil form
2. the need to wait for 16 warlock levels, with the dips in other lcasses you need to wait till Epics to play in the devil form

Hm. What are the other options for devil/demon shapechanging builds? I really liked the fluff of being a warlock/monk with commoner average physical stats, giving them a reason for making pacts with devil's and shapechanging into one.