Not at all. You may read in the description that it charms beasts. If you check the the information on any mobs/units, you will find their race (e.g. dragon, twisted, elemental, beast etc.) at the top, just below the unit name.

Hint: my advice is to try a great wolf... they are awesome at all stages of the game... a corpse spider is okay too. Umberdroths are quite resistant... but there are plenty other nice beasts around:).

Doubble click on the unit during a tactical battle and get it's unit card up. There it says what race it is. If the race is beast you can give it a try.

You can also get those unit cards up before battles on every unit you like, by choosing the unit in question, then press the unit portrait that comes up on the left side of the screen.

Huh, never realized I could do that. Thanks for the help guys!

Lucky me, I just found a Great Wolf den. Here's hoping to capture it!

Welp, I capture the Great Wolf, and then found another studded collar. Intentional? Or just damn good luck?

I also found an Umberdroth Lair, too.

I got the Umberdroth. Lady Luck is smiling upon me tonight! =D

I'm pretty sure the Collar is unresistible. I've never had it fail and I don't recall it ever showing any percentages like the 'Tame' spell does. This isn't surprising, since the Collar is a moderately rare piece of treasure, not a spell you can use every single battle.

I always get an Umberdroth or a Hoarder Spider with it. I find Great Wolves are far, far, far too distressingly squishy, and their late game use is fairly pointless; you'll be hitting everything like a damned freight train regardless.

The collar is one of my favorite items to get early on.  I usually try and get a bear or a great wolf or a warg.  All of them make wonderful companions in the early stages, especially when you start with no companions close by.

No, you've been doing that with a collar that probably wont work!  Ignorance is bliss!

I AM THE SPIDER GOD. THEY EAGERLY AWAIT THE SWEET EMBRACE OF MY COLLAR. ALL HAIL MY EIGHT FLAILING LIMBS.

No seriously, dozens of the damn things. Never failed. My Umberdroths and Hoarder Spiders all seem to be submissives waiting for the domme touch of my collar.

.....ew! My wildlife is perverted!

Guys, the collar can be resisted, but it's like other spells - it's a spell mastery vs spell resistance check.

If your sovereign is brilliant, wears some mage gear, and has a few levels under his belt, the chance of resisting is not that great.  If you are like me, and hoard the collar until you have a worthy target, you probably reach spell master 100, and have a only 3% chance of failure against most beasts.

That said, the most worthy beast of them all is the great wolf.  That howl is a game breaker, once you level the wolf.

IT can be resisted.  Spellcaster sovereigns have it much easier, which is kinda silly.