Finger of Death
Finger of Death cannot be countered by a Counter Spell. However, it can be reflected by a Magic Mirror. The surprise catch to this is that a Magic Mirror can be countered by a Counter Spell. So, if Bob casts Finger of Death and Counter Spell at Tim, and Tim casts Magic Mirror at himself, the Magic Mirror will be countered and the Finger of Death will still succeed; Tim dies.
Permanency, with one of the offensive enchantments (Confusion, Amnesia, etc.) will make the victim permanently afflicted. Another enchantment cast on the same victim on the same turn will dissipate the permanent enchantment, which will be wasted. However, another enchantment cast on the same victim on a later turn will have no effect, as the permanent enchantment overrides it. Note that permanent Amnesia or Charm Person not only makes it impossible to cast any useful spells, but also (unless your opponent is nice with Charm Person) makes it impossible to surrender.
Anti-Spell and Enchantments
After an Anti-spell, enchantments which cause duplicates of previous gestures will cause duplicates of the non-gesture caused by the Anti-spell, not duplicates of the gesture that was actually made that turn.
Two opposite Storm spells cancel each other out. An opposite Storm will destroy an Elemental and the Storm will be nullified. A same-type Storm will destroy an Elemental and the Storm will still take effect. A Resist [its own type] spell on an elemental will destroy the Elemental. A Fireball will destroy an Ice Elemental. Casting a Fireball upon yourself in the same turn as an Ice Storm will protect you.
Spells cast during a Hasted turn will start to time out at the end of that turn - a shield, therefore, won't last into the next turn at all, and an Enchantment's effect will be for use in the next turn.
Several enchantments cast upon a Hasted Warlock won't have an effect in the hasted turn; a Warlock will be free from Paralysis or Charm Person, as their opponent can't choose the target hand.
They will still, however, be affected by it in the next normal-time turn, and they will be affected in both turns by any of the other enchantments.
During a Time Stopped turn, no enchantments are in effect. Casting Time Stop upon a monster, therefore, will always allow the monster to hit its victim, as the victim's shield won't be present. Similarly, if you can complete a damaging spell during a Time Stopped turn, the victim cannot counter the spell. Other than this, a Time Stopped turn is equivalent to a Hasted Invisible turn.
Counter-spell and Monsters
Casting a counter-spell at a monster in the same turn as it is summoned (ie. targetting 'LH:Warlock') will not work. You can counter-spell the summoning by countering its target (counter-spell target 'Warlock'), but you cannot counter-spell a freshly summoned monster. Why not? Because counter-spell occurs before the monster exists. The same applies to Magic Mirror, for the same reason; see the spell order chart at the bottom of the Quick Reference page.
Summoning a monster targetted at another monster being summoned that turn won't work, even though Summon Goblin is stated to resolve before Summon Ogre - the Summonings are near-simultaneous, so the summoning that is targeted weirdly will fail. There is no reason to be doing that, anyway, since targetting the spell at the same target as the 'parent' monster will always resolve exactly the same as you might have expected from targeting it at the parent monster.
Blindness/Invisibility and Magic Mirror
Spells cast at a blind warlock who is covered by Magic Mirror will be reflected, but will not hit their original caster. Similarly, spells cast by an invisible warlock at a Mirrored warlock will be reflected but will not hit their caster. The Mirrored warlock must be able to see the target of the reflection to angle the mirror correctly.
Conversely, if a warlock is foolish enough to cast a spell at an opponent they can't see, and that target is covered by a Magic Mirror, the spell will be reflected back despite being aimed poorly.
Blindness/Invisibility and Dispel Magic/Remove Enchantment
Dispel Magic will not render an invisible opponent vulnerable, nor will Remove Enchantment make a blind warlock able to successfully target a spell that round - just as becoming invisible doesn't immediately make a warlock immune to attack. Creatures need a chance to re-orient on a known location.
To the Spells Quick Reference