As per topic above; every time I read the army list entry I'm confused.

As per pg 43 of the Greenskins book.

"[other text and then...] Finally, unless it was cast with IF, the spell auto-fails"

My interpretation of the relevant passage is...

NG shaman casts spell
then roll another die... this cant make the spell irrestible or cause miscast....roll a 1 and bad stuff happens to you...
finally; unless you rolled IF to begin with... the spell fails...

or am I just reading it wrong?

That's only if you roll a 1 on the bonus die.
Basically, if you roll a 1 on the shroom die, bad stuff happens and the spell automatically fails unless it was cast with irresistable force.
You don't roll a 1, it's basically like a bonus power die (without actually being a power die perse).

It is poorly worded though.

If you roll a 1 on the bonus dice, and then subsequently do not roll a 4+, the spell auto fails unless irresistible.
"On a 4+, nothing else happens" (Page 43)
If you roll a 1 on the bonus dice, and then roll a 4+, nothing else happens and the spell is resolved as normal.
Chances of it happening are one in 6 followed by one in 2 = spell fails unless cast with irresistible force.

ahh our interpretation at hampton is that on a 1 it fails, and on a subsequent 4+ nothing else happens.. nothing.. no spell... no destroying yourself, this is why my night goblin army doesnt run night goblin shamans anymore. just normal goblins in pointy hats

You roll for spell as normal. When done, roll another dice. If this extra dice comes up as 1 the spell auto fails (unless you got IF already). Roll dice again, 1-3 wizard takes a wound or 4-6 nothing happens.

NG shamans are great, because you get a free dice to use in the spell and the odds of it failing are very small

actually the odds of it failing are not that small, you HAVE to use the bonus dice you cant elect not to, so its a 1 in 6 chance of failing with EVERY casting, consider a level 4 might throw 2 or 3 spells out in a turn hes not gonna last long

True, but I have never used a lvl 4 yet. I run 2 lvl 1s, that cast their spell every magic turn. in the last few months of playing, have only ever failed it once

From the O&G FAQ;

Q: When a Night Goblin Shaman rolls a 1 on his Magic
Mushroom dice he has to roll again to see what happens. Does the
spell fail regardless of the result of this second roll (unless it has been
cast with Irresistible Force)? (p43)
A: Yes.

Lv1 or Lv2 NG shamans make great support, especially with their sneaky stealin' lore attribute. You use them to draw out dispel dice casting helpful buffs or hex's on one dice (plus one extra), then you smack 'em with lvl4 Big WAAAGH! spells. The odds of you auto-failing the spell are 1/3 sure, but then again so is the chance of you stealing one of their dice if you do cast, so I reckon its worth the risk. Tis only a single dice anyway, and I tend to swap out the curse and night shroud for sneaky stabbin anyway so the casting cost isnt that much. Gives you the most out of your scoll caddy anyway.

Arfa da Grate