It is 4th in my personal discard list. To clarify, mi Top5 is the one below:
- Duress
- Unmask
- Cabal Therapy
- Distress
- Hymn to Tourach
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Duress is far the best: low-costed, can take away almost any menace the Opponent should play.
Unmask has an excellent discard range, being able to get rid of creatures too, and a good alternative cost: being able to make our opponent discard 2 cards
whe choose on turn one (by making Duress+Unmask) can be an unvaluable starting; on the minus side, it is a bet to be played without being foreplayed by a Duress
Cabal Therapy is obviously great when you're able to Flashback it, but can be a good single shot discard if a Duress already hitted the opponent or if you know your oppo's deck and are worried about a given card (Cabal for FoW is always an option to be considered); great against bad players who Wish for a card without being able to play it (Way too common

)
Distress can get rid of any nonland card without the need of whiping away your own hand, but it's a bit too costed: CC 2 is not good, but BB is definitely bad, not allowing this card to be played in multicolored decks, thus making this worst that Unmask (since both are palyable only in Monoblack decks, maybe with a splash).
Tourach made history, but is nowadays not worth playing: way too many decks around that play using their own graveyard; what if I make a W-Mud player discard, to say, Triskelion and another random card, while he has a Welder in his hand? Or make a TPS player discard something that's nor Fow neither Y.Will? I think that aiming is better than quantity, so Tourach is going 5th