Misery has a limited upper bound because it doesn't do much in fights with single enemies in them, but it can often do some very impressive things in multi-enemy fights. Watch out for fights where enemies have their own debuffs which you can spread to the other enemies in the fight.
Spreading debuffs is quite fun but not as useful as you might hope. Unless you actually want a 0-cost attack you're better off with direct area effects.
Ethereal. The first Attack each turn deals 50% additional damage.
Gain 13 Block. Reduce this card's cost by whenever ANYONE dies.
Deal 7 damage. Apply any debuffs on the enemy to ALL other enemies.
Summon 5. Whenever Osty loses HP, ALL enemies lose that much HP as well.
whenever ANYONE dies.
