Ok so this is an idea that takes inspiration from one of the REALLY old design ideas of SK. WAAAAAY back in the day when SK was just coming together it was proposed that knights could pick up a piece of meat like a statue or totem. Monsters would focus entirely on this knight with the meat and would make it easier for party members to kill them. It was dropped since players would rather fight their way out of a horde of monsters rather than use some other more complex strategy.
So.... I came up with the idea to made a bomb that acts as a trap that uses the aggro mechanic.
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Name: Blackstar Nova
Damage: Shadow
Status: Fire
Charge time: Irontech equivalent
Detonation time: Greater than BAB but time remaining is reduced when hit by a monster.
Mechanics:
When you place the bomb it releases a small Fire Haze almost instantly. Monsters inflicted with damage by the fire will aggro at the bomb which is still counting down it's blast.
The detonation time on this bomb is very long, even longer than the BAB. Monsters can attack this bomb and doing so will chip off some time from the countdown (naturally it will have invinciframes). During the countdown the fire haze is active.
Once the bomb detonates it releases a massive explosion dealing high shadow damage and strong fire. It also has a 100% flinch chance on flinchable monsters.
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Uses:
This bomb is used to take out hordes of enemy monsters who will greatly accelerate the detonation timer by attacking the bomb. This bomb should prove effective against beasts, jellies, gremlins, and constructs.
It's a neat idea, very similar to the vortex bombs but also very different. I'd give this an A, because it's a very fun idea. I'd also love to see a piercing + shock variant of the idea; this unusual status combination would hit many undead and fiends harder while mucking up beasts a bit and allowing it to effect construct in some way. Since traditional vortex bombs don't work as well against fiends, this item could be made to do so.
I also do worry about the balance of this bomb compared to ash of agni and the vortexes however. To be specific, it would charge faster than ash of agni light them on fire, clump them in the middle (most of the time) and then deal better damage than graviton vortex. I could be mistaken, and the balance could work out, but here's how I would have done it-
Balance Suggestion
Charge time: Vortex/Haze equivalent
Detonation time: Greater than BAB, same as above
Status/Damage variations: Shadow+Fire, Piercing+Shock
Mechanics:
Stage One-
Has a very large initial blast (twice the size of nitronome) that draws in all aggro to the center of the bomb. Enemies can still lose aggro and refocus on knights.
Stage Two-
The monsters either kill the bomb or time runs out, releasing a massive explosion. This explosion would be identical to irontech destroyer, but with the damage type and status changed to fire/shadow or shock/piercing.