Whenever an RPG is modeled after another work, as the DFRPG is, one of tests it must satisfy is: Does the game accurately model the common events and situations that occur within the context of the original work?  For the most part this game succeed in that.  However, I find that it falls down somewhat in terms of "The Catch" the required vulnerability that balances Toughness related powers.

As worded a "Catch" is something that bypasses a being's supernatural defenses to inflict injury upon him or her.  A werewolf shot with a silver bullet will tend to take far more damage than one shot with a normal bullet.  Not only that, the wounds of a silver bullet are not affected by the werewolf's supernatural ability to recover.  Thus, a werewolf will take longer to heal the consequence of being shot by silver.  So far, so good.

The problems comes when the "Catch" seems to do far than simply act as an equalizing vulnerability.  Consider the White Court vampires and their Catch of True Love.  In Book 6 Thomas Raith tells Harry about this weakness and describes a situation in which Lara is so badly burned by a wedding ring that it left a permanent scar on her hand.  Note the context here.  Lara wasn't slapped by a person wearing the ring in a damaging attack.  The ring was presumably an object that Lara picked up.  Furthermore, we get a demonstration of the full effects of Love in Book 11.  When Justine kisses Madeline and sweeps her hair down Madeline's body, Harry describes the effect as being similar to a strong acid being poured on her skin.  Finally, along with dealing actual damage, Love makes a person immune to a White Court vampire's greatest power, the ability to induce specific emotion in their prey and use those emotions to feed upon their victim's life force.  That's not a Catch.  That's a net made from fishhooks and barbed wire.

So, I would recommend introducing an upgraded version of the Catch called a Bane.  Banes are built much in the same way as Catches in terms of the availability and secrecy of the Bane.  Banes have other aspects depending on what they do.  A Bane that disables or provides immunity to powers worth a fourth or less than a character's modified Refresh cost for that suite of powers(1) or less is worth 0 points.  One that disables or provides immunity to powers with at least half Refresh cost for the suite is worth +1.  One that disables or provides immunity to at least three-quarters of a suite's supernatural abilities is worth +2.  Note that since a Bane is already a Catch, Toughness Powers aside from Immunity to Damage are not considered part of a power suite's refresh cost  A Bane may also have a damaging aspect, the strength of which is determined in the same way as the disabling effect was with the modified Refresh rolled as an attack against the target's Endurance with the modified Refresh as damage (or even damage modifier).

Example: Kevin, a former Changeling who Chose to be human, is being chased by a couple of Winter Sidhe who some payback for things he did before his Choice.  The Sidhe have Glamour(-2), Inhuman Speed(-2), Strength (-2), Toughness(-2) and Recovery(-2) for a total modified Refresh of (-6) and they have both a Power Loss and Damage Bane to Iron/Steel.  Kevin ducks into a chop shop with the two Fae in pursuit.  As they enter, Kevin a can of nuts and bolts and hurls the contents at them.  The second Fae dodges back, but the first is hit.  Normally, this tactic would at be a maneuver or distraction, but these are Fae and their Bane is iron.  So, not only does Kevin get the benefit of the maneuver, he cause Fae 1 to temporarily lose his powers and applies a Damage 6 hit plus Shifts.  Fae 1, shrieking and blistering, flees.  Which gives Kevin time to grab his trusty crowbar and swing it at Fae 2.  Successful strikes with this weapon will be Damage 8 (Weapon 2 plus Bane damage 6) and will apply consequences of Power loss.  Assuming he survives, Fae 2 will probably rethink coming after Kevin again.  Directly, anyway...

The final aspect of a Bane is Range.  If a Bane is only effective if deliberately deployed as a maneuver or weapon, its worth is 0.  If it's effective in melee range (touch or up to five feet) it's worth +1.  It's it's effective up to 60 feet or so, it's +2.

There is one other consideration for Bane and that is the Bane Limit.  It should be obvious that someone could use the Bane rules to put together a ridiculously large Refresh cost break and build characters far in excess of a campaign's normal refresh limits.  The potential Refresh rebate for the Fae in the above example would be +10 (+2 for common item; +1 for research needed (Fae aren't quite as well known as werewolves and vampires); +2 for Power Loss (Fae lose most their non-human powers at the touch of iron); +2 for damage (iron hurts a lot);  and +1 for range (it does, however, still have to touch them to be effective).  The Bane Limit is the (Refresh Cost of a power suite's abilities - (bonuses for other limitations (human form, feeding dependency) + Toughness powers))/2 rounding down.  For our Fae up there that would be a 3.  The total Refresh cost is 10.  Subtracting Recovery and Toughness yields 6.  6 divided by 2 is 3.  Which doesn't seem like a lot considering the ways in which iron can screw these Fae up.

The thing to remember is that characters change a grow .  Suppose our Fae improves his Glamor to Greater Glamor, a -2 Refresh cost.  With that ability, his Bane Limit grows to 4 (Refresh cost - toughness)/2.  Thus a 1 point increase in Refresh could allow our Fae to effectively gain a 2 Refresh cost ability.  Note as well that Banes can increase.  Perhaps a Changeling with a simple Catch of iron could see that Catch become a nasty bane as he gains more and more power of the Fae, becoming more sensitive to Iron as he grows less and less human.

A character can have multiple Banes, but just like Catches, only the most potent give a Refresh break.  Multiple Banes can, however, be quite useful as potential Compels, especially for those who like to live close to the Refresh edge and need those extra Fate points.

(1) A Power suite is a set of powers linked to a particular High Concept like Changeling, Werewolf, White Court Vampire, etc.  Suppose Billy the Werewolf had a total Power Loss Bane to Silver.  Suppose further that some bizarre circumstance caused him to be gifted (cursed?) with The Sight(-1) and Soulgazing.  If Billy were shot by a silver bullet he would immediately transform to his human form and not even have his increased sensory perception (Echoes of the Beast) until the bullet was removed.  He would, however, still have The Sight/Sougazing because those are not part of the werewolf power suite.