Raspen said:
is it possible to use a free action, a move action and still hold your standard action to ready a counter spell?
Yes, in most cases.
and can I cast invisibly on myself to counter the effect of targeted spells that are aimed at me?
Not a "counter" exactly, but a DM may let you
ready an Invisibility spell to cast when someone else begins to cast a spell. Thing is, the DM might also say it is too late to cast an actual spell if you wait until you Spellcraft ID the spell being cast and IMO the DM
should say it is too late if you wait to be
targeted by the spell.
or use a wall of fire as a readied counter spell to block vision?
That is not a counter spell. See above.
Ready action is not an open license to do whatever is in your best interest when the time comes. You must specify the action you will take and the conditions under which you will take it when you ready.
READY
The ready action lets you prepare to take an action later, after your turn is over but before your next one has begun. Readying is a standard action. It does not provoke an attack of opportunity (though the action that you ready might do so).
Readying an Action: You can ready a standard action, a move action, or a free action. To do so, specify the action you will take and the conditions under which you will take it. Then, any time before your next action, you may take the readied action in response to that condition. The action occurs just before the action that triggers it. If the triggered action is part of another character’s activities, you interrupt the other character. Assuming he is still capable of doing so, he continues his actions once you complete your readied action. Your initiative result changes. For the rest of the encounter, your initiative result is the count on which you took the readied action, and you act immediately ahead of the character whose action triggered your readied action.
You can take a 5-foot step as part of your readied action, but only if you don’t otherwise move any distance during the round.
Initiative Consequences of Readying: Your initiative result becomes the count on which you took the readied action. If you come to your next action and have not yet performed your readied action, you don’t get to take the readied action (though you can ready the same action again). If you take your readied action in the next round, before your regular turn comes up, your initiative count rises to that new point in the order of battle, and you do not get your regular action that round.
Distracting Spellcasters: You can ready an attack against a spellcaster with the trigger “if she starts casting a spell.” If you damage the spellcaster, she may lose the spell she was trying to cast (as determined by her Concentration check result).
Readying to Counterspell: You may ready a counterspell against a spellcaster (often with the trigger “if she starts casting a spell”). In this case, when the spellcaster starts a spell, you get a chance to identify it with a Spellcraft check (DC 15 + spell level). If you do, and if you can cast that same spell (are able to cast it and have it prepared, if you prepare spells), you can cast the spell as a counterspell and automatically ruin the other spellcaster’s spell. Counterspelling works even if one spell is divine and the other arcane.
A spellcaster can use dispel magic to counterspell another spellcaster, but it doesn’t always work.
COUNTERSPELLS
It is possible to cast any spell as a counterspell. By doing so, you are using the spell’s energy to disrupt the casting of the same spell by another character. Counterspelling works even if one spell is divine and the other arcane.
How Counterspells Work: To use a counterspell, you must select an opponent as the target of the counterspell. You do this by choosing the ready action. In doing so, you elect to wait to complete your action until your opponent tries to cast a spell. (You may still move your speed, since ready is a standard action.)
If the target of your counterspell tries to cast a spell, make a Spellcraft check (DC 15 + the spell’s level). This check is a free action. If the check succeeds, you correctly identify the opponent’s spell and can attempt to counter it. If the check fails, you can’t do either of these things.
To complete the action, you must then cast the correct spell. As a general rule, a spell can only counter itself. If you are able to cast the same spell and you have it prepared (if you prepare spells), you cast it, altering it slightly to create a counterspell effect. If the target is within range, both spells automatically negate each other with no other results.
Counterspelling Metamagic Spells: Metamagic feats are not taken into account when determining whether a spell can be countered
Specific Exceptions: Some spells specifically counter each other, especially when they have diametrically opposed effects.
Dispel Magic as a Counterspell: You can use dispel magic to counterspell another spellcaster, and you don’t need to identify the spell he or she is casting. However, dispel magic doesn’t always work as a counterspell (see the spell description).
