So after having a hunt last week ended because I got hit by (what used to be a Cleric spell, and is now on the critter-only list), 'Interference'...
...(which, if you don't recall, works by sucking all of your mana away, thank you for playing, do come again).

I took that lesson to heart and, well, learned from it.

.

This evening's Shaman, his work on me, and my response.

---

An Illoke shaman calls forth the wrath of his god as he points at you!
CS: +282 - TD: +220 + CvA: +3 + d100: +40 - -5 == +110
Warding failed!
The spirits swirl around you, distracting your every action.
>
You sing with renewed vigor!
An Illoke shaman appears to be struggling with the debilitating force!
CS: +308 - TD: +259 + CvA: +20 + d100: +14 == +83
Warded off!
An Illoke shaman is unaffected.
Renewing "Song of Depression" for 6 mana.
Sing Roundtime 3 Seconds.
>
You sing with renewed vigor!
An Illoke shaman appears to be struggling with the debilitating force!
CS: +308 - TD: +259 + CvA: +20 + d100: +60 == +129
Warding failed!
An Illoke shaman appears slower and looks depressed.
Renewing "Song of Depression" for 6 mana.
Sing Roundtime 3 Seconds.
>
An Illoke shaman swings a massive granite hammer at you!
AS: +362 vs DS: +431 with AvD: +32 + d100 roll: +59 = +22
A clean miss.
>
You currently have the following active spells:
Spirit Warding I ................... 3:43:12
Spirit Barrier ..................... 0:25:08
Spirit Defense ..................... 0:03:15
Disease Resistance ................. 3:43:19
Poison Resistance .................. 3:43:22
Spirit Warding II .................. 3:43:26
Spirit Shield ...................... 0:08:29
Elemental Defense I ................ 3:44:47
Elemental Defense II ............... 3:44:47
Elemental Defense III .............. 3:44:47
Elemental Targeting ................ 3:44:47
Elemental Barrier .................. 3:44:47
Thurfel's Ward ..................... 3:44:17
Strength ........................... 3:44:13
Resist Elements .................... 3:42:51
Mobility ........................... 0:58:23
Mass Blur .......................... 3:44:22
Fortitude Song ..................... 0:06:06
Song of Luck ....................... 0:06:00
Song of Valor ...................... 0:06:03
Song of Power ...................... 0:05:57
Song of Mirrors .................... 0:05:53
Interference ....................... 0:00:48
>
prep unravel
>You speak quietly in flowing elven, preparing the Song of Unravelling spell...
Your spellsong is ready.
>
cast at <my bard> interference
>You weave another verse into your harmony.
CS: +308 - TD: +259 + CvA: +3 + d100: +91 - -5 == +148
Warding failed!
You find a thread matching the harmonics of your song and pull it loose.
The distracting force passes away from you.
Your concentration on unravelling the threads of mana is broken.
Sing Roundtime 3 Seconds.
>
An Illoke shaman mutters a prayer to his god.
>
You speak quietly in flowing elven, preparing the Vibration Chant spell...
Your spellsong is ready.
>
You weave another verse into your harmony, directing the sound of your voice at an Illoke shaman.
CS: +308 - TD: +229 + CvA: +20 + d100: +80 == +179
Warding failed!
You focus your voice on an Illoke shaman's iron shield with perfect resonance, causing it to shatter into thousands of tiny pieces!
... 40 points of damage!
Hard blow to neck loosens head on shoulders.
Quite fatal!
The Illoke shaman rumbles in agony as he teeters for a moment, then tumbles to the ground with a thundering crash!
The Illoke shaman shudders one last time before lying still.
An Illoke shaman glances around, looking a bit less confident.
An Illoke shaman seems hesitant.
The brilliant luminescence fades from around an Illoke shaman.
The bright luminescence fades from around an Illoke shaman.
The air about an Illoke shaman stops shimmering.
The silvery luminescence fades from around an Illoke shaman.
Sing Roundtime 3 Seconds.

---

I find it interesting that I only have about a 50/50 chance of removing a spell from myself.

>I find it interesting that I only have about a 50/50 chance of removing a spell from myself.

It looks like you have to ward the Shaman's TD (which is rather higher than yours) in order to remove that spell.

That's probably built into the spell effect riding on the character, because the last time (when the mana got drained way later) I walked away, so the caster wasn't even in the room.

.

And in fact, it's confirmed that it is built into the spell effect, because by the time I got around to doing the Unravel, the shaman was already subject to my Depression [-20TD + -10TD more due to Lore] effect.

In addition, Estild, that spell effect is listed as 'Interference' (as shown in the log). However, Interference is now the Cleric spell 212; the creature ability is called 'Interdiction'.

Should one or the other (probably the critter-cast one) be renamed? In case, say, an actual Cleric casts an actual 'Interference' effect?

According to the Wiki, and the description thereon, it is called Interdiction.

However, per the log, 'spell active' thinks that it is called Interference.

'unravel <mychar> interference' worked just fine, as demonstrated in the log.

Mana-drain stopped.

So did the shaman, 3s later. :)

I'll be honest, I jumped to the conclusion that it was <the nasty thing that ended my hunt the previous week>, rather than possibly some entirely different spell (and even with the correct name!).

Thanks for clarifying!