Slow withering

When slow withering is in play do you have to pay the extra cost even when playing the card at inferior if thee card has an at superior option? Like playong Thon Blood at inferior.

The effect of Slow withering (paying extra) only applies for playing cards at a superior discipline. The "requiring/requires" word is a bit misleading sometimes, but you get used to it.

"Requiring" can also for example be found on True Brujah: "xhe cannot use cards requiring Celerity". However, True Brujah CAN use a multi-discipline card with a potential (unused) Celerity effect, for example Make the misere on obf+pot. But not cel.

Name: The Slow Withering
Cardtype: Event
Gehenna. Requires 1 or more other Gehenna events in play. Do not replace until a vampire commits diablerie.
Cards requiring 1 or more Disciplines at the superior level cost +1 blood. Vampires who commit diablerie ignore this effect until a Gehenna event is played.

Name: Make the Misere
Cardtype: Action
Discipline: Celerity/Obfuscate/Potence
Requires an Anarch. More than one Discipline can be used to play this card. Enter combat with a locked minion.
[cel] This Anarch gets 1 optional maneuver during that combat.
[obf] This is a +1 stealth action.
[pot] This Anarch gets +1 strength during that combat.