Thanatosis is quite a weird discipline, and some say it fails to do anything really useful. Let's get to the bottom of it with these comments by Arpèges and Orpheus.

Card
Cost
Card Text
Comments
Ratings
Ashes to Ashes
[for]: Only usable by a vampire being burned; he or she is sent into torpor instead. [than]: Prevent all damage. This vampire untaps and goes to torpor (ending combat). [THAN]: As [than] above, and this vampire gains 2 blood from the blood bank.
In the case you don't play your Samedi as a clan but as a support to a strategy, this card may be as useful as may be Reform Body in Vic. That is to say : very cornercase.
Compress
[pot]: Strike: strength+2 damage. [than]: Strike: 2 aggravated damage. [THAN]: Strike: 3 aggravated damage.
One of the reasons why Samedi are feared. A bit expensive, though, when it can be dodged or prevented. Only solution : play it right after a Withering, and then you'll be really fearsome !
Dust to Dust
[obf]: Press, only usable to end combat. [than]: Strike: dodge, with an optional press. [THAN]: As [than] above, with an optional maneuver.
As for Ashes to ashes, fits well in a "Samedi are cowards" deck. Cornercase
Hag's Wrinkles
Only usable on an equip action. [obf]: +2 stealth. [than]: Untap this acting vampire if the action is successful. [THAN]: As [than] above, but with +1 stealth.

Arpèges : Excellent. The new NRA allows you to take as much equip action you may like. This card allows you to use at best Pier 13.

Orpheus : I disagree. This is pretty cornercase for a Clan which can use Freak Drive on any action, or Disguised Weapon for equipping. Very cornercase IMO.

or

Infection
[for]: Prevent all damage from the opponent's strikes this round. [than]: Prevent all damage to a ghoul (ally or retainer) in combat. Usable by a vampire not involved in the combat. [THAN]: Only usable at the end of a round in which this vampire successfully inflicted damage on the opposing vampire. Put this card on the opposing vampire. The vampire with this card cannot block the vampire playing this card.
May be useful in any deck that doesn't rely only on combat, but a bit too expensive.
Putrefaction
[pre]: Strike: combat ends. [than]: Strike: 1 damage. Put this card on the opposing minion. The minion with this card has -1 stealth. He or she may burn this card instead of untapping as normal during his or her untap phase. A minion may have only one Putrefaction. [THAN]: As [than] above, and this minion takes 1 unpreventable damage when he or she strikes in combat or takes an action. The minion with this card may choose not to strike during the Choose Strike step of combat.
Would be good if it cost no blood at all. OK, Samedi have fortitude, but either you drain all your vamps in a combat, or you play tons of prevent. That is not an option.
Rigor Mortis
Only usable before range is determined. A minion can play only one Rigor Mortis each round. [pre]: The opposing minion cannot use any additional strikes this round. [than]: As [pre] above, with an optional press. [THAN]: As [than] above, and once each round, you may cancel a maneuver used by the opposing minion..
In a combat deck, this card kicks ! It allows you to take control of the combat. Would be better for no blood, though. Can be useful in Inf for the Brujahs, if they have blood to spare.
Withering
[ani]: Strike: 1R damage. [than]: Strike: strength damage. Place this card on the opposing minion. The minion with this card has -1 strength. Burn this card during his or her controller's next discard phase. [THAN]: As [than] above, and the minion with this card cannot play cards that require any disciplines.
The best combat card of that discipline. Play with trap, and burn any vamp. Hidden lurker will prevent your opponent to play S:CE. Of course, he would have to block first...