So this card (and it's coupled weakness Bloodlust) is a bit confusing, so I'm going to give a quick summary here so that you don't have to switch between the two cards's pages:
- The Hungering Blade by itself give no extra and does +1 damage. It's closest equivalent is a .32 Colt: same cost, same lack of extra , same damage. Just without limited uses and you're allowed only one copy in your deck.
- To get the full power of this card, you need to kill six enemies with this amount of damage and draw the three Bloodlusts that got shuffled into your deck; doing so takes your Colt and upgrades it into .45 Automatic, then a .45 Thompson, then a Roland's .38 Special (clue included).
- HOWEVER, at any point you have a Bloodlust attached to The Hungering Blade, you may expend one Bloodlust to give your attack a further +1 damage; I'm fairly certain this cant be done after the skill test, so this is equivalent of -1 for +1 damage.
This actually reminds me of the good old core set Knife; two options for an attack, one standard, and one with extra damage but you discard something. And just like Knife, not utilising the secondary attack is a waste of the cost to play it. If you're using The Hungering Blade, then you should have a decent chance of succeeding combat checks from the moment you equip it, otherwise you'll be hard pressed to get those offerings. The extra then is a nice bonus, but not something you should be relying on, especially since +1 damage is more valuable than +1 attack.
Now about the horror incursion. Despite being the most suited for extra damage without extra , Mark Harrigan CANNOT take this card; doing so would be suicide alongside Shell Shock. Given that the other 5 investigator cannot take it, and anything less than 4 would leave one struggling to get offerings in the first place, the list of viable investigators shrinks to the rest of the guardians (that aren't Carolyn Fern), Joe Diamond, and William Yorick: 6 total. Even so, NONE of the investigators mentioned above have higher than 6 sanity, and given the random nature of your deck, you are subject to the whims of fate with this card (I mean, even more so than usual).