Cost: 5.
Test Icons:

Choose either your location or a connecting location. Deal 3 damage to each enemy and to each investigator at the chosen location.

Dimitri Bielak
Core Set #24.
Dynamite Blast
FAQs (taken from the official FAQ or FFG's responses to the official rules question form)
  • When you play Dynamite Blast while engaged with enemies, first you spend an action and pay the cost, then each engaged enemy makes an attack of opportunity against you, and then the effects of the card resolve -- but only if you're still alive. If the enemies' attacks defeat you, the effects won't resolve.
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This seems to be a staple in many protector decks, but truly this card is better used by evasive characters who can disengage or use teleportation cards (such as Elusive or Survival Instinct ) to launch Dynamite from an adjacent room.

While it certainly feels heroic to use Zoey or Roland to draw aggro then blow themselves up, it's often detrimental to the party's success to willingly subject them to 3 damage. Sure, it can sometimes save the scenario, but just as often it can place your best monster-hunter on death's doorstep.

It's far more effective to place it in the decks of the swifter investigators who have resources to spare (Skids, Jenny, Rex) and let them play with the explosives. If the enemies survive then the protectors job is to come back in the room and do clean up.