Can an Assassin add new spells to his available list, other than from leveling up?

Say he finds an arcane scroll of "Knock"...quite handy for an Assassin, no?

Another question from me in long series of ToB related questions.

Stances are swift actions.
Counters are immidiate actions.

Can both be used at the same time?

Since he is a spontaneous caster, just like a bard, he could get more "spells known" by buying Knowstones (items that featured in Dragon Magazine, so your DM might not allow them).

However, "Knock" is not on the Assassin Spell list. That means assassins don't have access to that spell, ever, just like a bard couldn't get access to a sorcerer/wizard spell that isn't on the bard spell list. Technically, an assassin can't even cast a scroll of "Knock" without making a UMD check.

Once you initiate a stance, you stay in that stance until you decide to change. So you use your swift action first thing in the morning when you wake up, and just walk around in that stance all day long. So you still can use counters as needed. But obviously you cannot use a swift action (or change your stance) in the turn immediately following when you just used an immediate action.

Hmm. Can you do it the other way around? That is, use an immediate after you've activated a stance?

For example, a Swordsage gets into his Holocaust Cloak stance, then a minotaur charges him on the same round (the Swordsage has better init). Can the Swordsage use Counter Charge?

That's not the other way around. That's exactly the way I described it: Stance first, then counter.

You misunderstand. All that, was in the same round. The EXACT same round.

Yours is more of a question of how swift and immediate actions work then. You can pretty much always use a swift action on your turn and then an immediate action on your foe's turn.

So let me get this straight, if the swordsage wins the initiative and uses a stance and then uses a counter against an enemy that attacks him on the second round he will be forced to drop him stance, correct?

On the other hand if on the first round the swordsage loses initiative and uses a counter against an enemy that attacks him then he will not be able to use his stance?

Your first example is wrong-once activated, Stances require no actions to maintain, so they essentially remain active until you fall unconcious or activate a different stance. Your Swordsage could enter a stance, and then counter, and still keep his stance.

The second one is correct. An out-of-turn immediate action costs you your next turn's swift action.