Player A casts Mind Steal on player B and chooses one of his Spells to take. If player B still has Mind Steal, then he can cast it after the Mind Steal has ended!

ok but the problem was another one:

player b hold in his hand "spell call" that says: " Cast immediately after any character casts a Spell . Instead of placing the Spell on the discard pile, you may take it"

so the opinion of player B was that he can use that spell, so it wasn't available for player A, bound to choose only the other spall in the player B hand.

Player A argue, instead, that he was able to choose both the spells, beacuse, in his opinion, mind steal allows him to choose one of both the spells and player B couldn't launch spell call in this case.

When player A has taken the Spell of his choice from player B, player B can then cast Spell Call (if he still has it) which allows him to take the Mind Steal Spell instead of it being place on the Spell discard pile. To prevent Mind Steal from working, a character must cast either a Counterspell or Reflection Spell. You cannot counter Mind Steal with Spell Call; the Spell which has just been cast must take effect!

Ell.

Ok, following your opinion, player B argue this: why spell call, that says: " Cast immediately after any character casts a Spell . Instead of placing the Spell on the discard pile, you may take it"

can't be used after mind steal, in the same way whan you use it after any other spell? and, following this opinion, also nullify must take effect before you use spell call?

edit: to clarify ... it's a spell call, so you "call" any other spell ... like counterspell, you "counter" any other spell, but why, in your, and player A, opinion, you can "counter" any spell, but not "call" any spell? ^ ^ this is player B argue

Basically, this game isn't Magic: The Gathering. When a card refers to a spell being "cast," it means the spell is "cast and its effect resolved." Spells are cast and fully resolved one at a time. If a spell seems like it's played in response to another spell, the first spell is resolved completely first, then the second spell can be played in response - once the effect of the first spell has been completed.

The rare exceptions are those spells which prevent the effect of a spell from occuring, like Counterspell. But those spells will say so explicity. Most of the time, if a spell is played in response to another spell, it means in response to the spell after its effect is resolved.

Basically, this game isn't Magic: The Gathering. When a card refers to a spell being "cast," it means the spell is "cast and its effect resolved." Spells are cast and fully resolved one at a time. If a spell seems like it's played in response to another spell, the first spell is resolved completely first, then the second spell can be played in response - once the effect of the first spell has been completed.

The rare exceptions are those spells which prevent the effect of a spell from occuring, like Counterspell. But those spells will say so explicity. Most of the time, if a spell is played in response to another spell, it means in response to the spell after its effect is resolved.

Good summary.

I only wish to add that a Spell cannot be cast after another Spell if the resolution of the first Spell unvalidates the casting conditions of the second Spell.

My personal Spell Golden Rule:

Don’t react to Spells by casting Spells, except with Counterspell or Reflection.

as previous mention all spells that are cast have effect, then the next spell can be cast which also has an effect. a spell can not be cast that has no effect.

so in this situation

mind steal is cast. mind steal effect happens caster choses the spell to be taken

if spell call is still in hand then after the effect of mind steal is resolved, then that spell can be cast.

the only way to stop a spell effect from happening is to either negate it with counter spell (negates the effect of a spell just cast) b reflection( reflects the spell upon the caster) and there may be other such possibles negation type spells.