Thoughts on Crystal Bomb?
I've seen one of these in action and wasn't particularly impressed, plus being a piercing weapon means that it wouldn't make much sense to pair it up with my Thorn Blade although until I reach problems in tier 3 with my Winmillion, that won't be a problem. I never really gave thought to being a bomber at all but my luck streak at the Jelly Palace has been continuing and after finding a Brute Jelly Shield, I found a Crystal Bomb. So is it worth using at all? If it is then which line would be better to upgrade into? Ionized Salt Bomb has a damage bonus against Slime which laps with my Chroma line and gives Piercing and Normal damage which seems better than Elemental and Piercing though I may be wrong.
Definitely sun shards, although I think the crystal bomb is kinda junk anyway.
I don't need help fighting fiends though they're all straightforward. The only one's that are any slight bit of trouble are the Greavers since they're fast but I won't get a chance to hit them with a bomb.
if you've seen one in action, then yes, you have no cause to be impressed. the crystal bombs are great for soloing. when you have 3 other players running around knocking monsters around with swords, then its very hard to catch enemies in the shrapnel spread.
By yourself however? this bomb murders beasts. I solo jade tangles and wolver dens with this bomb constantly, dont even switch weapons. The best thing about it isn't its damage or how it spreads out or the shock if you go ionized shock, the best part is that whatever it hits gets knocked down, as if it got wacked by a full series of sword hits. with just a little CTR, that's actually just enough time to charge up the next one, plant it, and do it again. Anything you can catch with a crystal bomb, you can control with a crystal bomb. You won't kill it that fast, but it won't be able to hurt you either.
Also, any monster that you can get to step directly onto the bomb when it explodes will get hit by every shard. this instantly kills most monsters while soloing.

+Radiant Sun Shards is fast. It shares the fastest charge time in the game with Nitronome and DBB. If you've ever used a blast/nitronome or DBB you know that you can deploy it very quickly when running a mad bomber or mixed set (volc+mad bomber). The charge time is so fast in fact, that you can prep a bomb while being chased by greavers and put it down before you get hit. On top of that, it has the fastest fuse of any bomb (I haven't measured this but I'm pretty sure)
+Radiant Sun Shards does a ton of damage*. When you hit an enemy with 2+ shards it out damages haze, blast bomb, and DBB (assuming neutral or bonus damage i.e. construct, fiend, etc). Multiple shards means you can break 3 hit blocks instantly as well as breaking down minerals with just one bomb (a must for pure bombers!)
+ RSS huge range on the shards. If you're pure bombing this is great for hitting switches.
- *Somewhat inconsistent. One of the big problems with RSS is that it shoots out 8 shards in predetermined directions. You're somewhat at the mercy of geometry here so while you can out damage a blast bomb you can't do it all the time. If you place it wrong you're only hitting once. If you place it right you could hit 4 times. If they step on it you could hit 6 times but you shouldn't rely on this because there is no way you'll maximize damage on every bomb.
- Diminishing returns. Another problem with the RSS is as you dwindle the number of enemies down (assuming not large targets like lumbers), you hit diminishing returns much faster than other bombs. This is mainly because you're shooting shards in 8 directions and it gets easier and easier to for you to start missing all your targets. For smaller numbers RSS gets very, very inefficient compared to other bombs and that's saying a lot because bombs in general are pretty inefficient against small groups of targets.
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As for actual use, I like the RSS against undead (zombies, ghosts) and greavers mostly. It is pretty satisfying to drop a RSS and get surrounded by greavers then have it blow up and hit all of them 3-4 times. For ghosts it is a similar deal since they both do a lunge attack that closes in on where you last were. For beasts I think the nitronome and DBB are much higher DPS since you'll be hitting EVERY target in a radius rather than being at the mercy of shards. Devilites are kind of hit or miss (literally, lol!) The DBB and nitronome are a lot better. For trojans the sun shards are pretty good but the fast fuse actually hurts it here because it will go off before you can spin the trojan around a lot of times. As a result, to deploy RSS successfully against a trojan you'll have to run around until the trojan pauses and then drop it but I find sword charge attacks are better suited since you'll have enough time to charge them and they'll out damage the RSS anyway, even if you hit 3x.
I would really like to see a 5* RSS with 8 shards and the addition of a smaller super/master blast bomb sized explosion which would make it a lot more consistent/reliable.
As for ISB, I don't recommend it. It has a long charge which hurts a lot. If you're not wearing bomber armor I wouldn't recommend building this bomb AT ALL. It doesn't do a lot of damage, shock has been nerfed enough to make the long charge not make any sense. I find normal/pierce isn't a very strong combo and the slime bonus makes no sense since they're strong to slimes.
tldr: skip the ISB. build the RSS for fun but there are probably better bombs if you just want a DPS bomb to main
...and Sun Shards are really good at killing Fiends.