Support gem - Cast On Hit

Small idea for a support gem, which has been tickling me for a while now:

Support gem

Cast on Hit
Color: red
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Provides a chance to cast one of the linked spells or curses on hitting with an attack

Base chance to trigger: 15%.

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On level: +1%

Quality provides +1%



Assuming 20% quality, a maxed (level 20) gem would have 55% chance of casting the skill on attack, which is huge, but... it's a level 20 quality 20 gem. It's huge by default. Without quality, it only has a 35% chance of triggering, which is decent, I think.
Only works on the first attack; pierce and fork does not spread the effect.

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The main uses I can see for this would be a huge buff for elemental Templars and Shadows, or on Marauders and Duelists for the crowd control. On hit triggering Ice spear + fork + chain + multiple shot would be an amazing combo, though at the cost of quite a few linked sockets. Auto-casting curses, or something like frost nova, would be good too. The biggest thing is: this doesn't slow down your DPS by forcing you to cast a spell in the middle of combat. It also ignores your cast rate.

Would work amazing with Sweep or Etheral Knives.

Opinions?

I think this is the gem everybody is waiting for. Some more suggestions on its actual implementation.

I don't know if its possible to link a skill gem to another skill gem through a support gem. If it is not, cast on hit could be a skill gem and you need to link a spell to it. Using it would be using the base attack + (a chance to) cast the linked spell.

An alternative would be a pre-determined spell in a support gem. A "cast nova on hit" gem for example. It would be a set of support gems as well. It does reduce the possibilities but makes it a bit easier to balance some spells.

To keep it all balanced the linked spell (particularly if it can be linked to an attack skill) has to be balanced some way by: mana cost multiplier, reduced damage of the spell, chance to cast and/or max number of casts per 10 seconds come to mind.

I can see why this is an appealing support gem, but i think it may be hard to implement.

First having a glacial hammer that sparks combines two powerful attacks to one strike - so I would expect at least -50% dmg for each added skill (otherwise the balance is just ruined)
I can imagine these "on hit" skills to be triggered by the standard attack to reduce this problem.

Second the combo above also combines single and multiple target attacks, moving the game in the direction of "one-Button-Click", a way the devs clearly stated they want to avoid

third think of a 6L Armour with cleave, the support gem and 4 spell or projectile attacks added - to balance this would be a nightmare i think.

fourth as talking of projectiles, i would find it unfair to work for magic but not for arrows ...


But i support the notion of "on hit" effects, these were the ones that made exotic builds much more fun in D2 than anything else. But as in D2 I see them more on gear than as gems.


€: maybe "on hit" skillgems could be implemented as separate skillgems "cast frost nova on hit" like doemaarvat stated. I REALLY like this way. I can even imagine a currency item that allows you to turn a skill gem into an on hit skill gem and back ...

Instead of increasing chance by level and by quality why not consider a 100% chance but with increased manacost for spell and also not casting it if you haven't enough mana?
Level would increase damage/strength of spell and quality would decrease manacost multiplier.

Opinions?

Should be veeeery expensive but fun!
I'd like to see cast on BEING hit, which is what I thought when I read thread title. You get hit for >1 damage or just hit I'm not sure - you cast eg shock nova. Would be fun for low evasion chars, and should be blue.

Would work if it simply converted the connected skill(s) into a castable permanent buff (like an aura), and that buff caused you to have a chance to use the skill on hit, as well as adding any necessary drawbacks.

IMO +1000% add this <3

Limiting the damage of the spell by 50% or 75% would work to balance it out, I think. But honestly, that "orb that turns gems into on hit and back" idea looks interesting as well...

It could even be activated. How about this:
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Orb of Impact

Rarity: high
Affected Gem can only be cast on hit. 15% + 1 per quality of gem chance of casting per hit.
Once triggered, affected skill has a 50% chance +1 per quality of being cast per hit for 10 seconds, but falls on cooldown for 1 minute.
When on cooldown, the spell cannot be activated.


--

Orb of Retaliation

Rarity: high
Affected Gem can only be cast on being hit. 15% + 1 per quality of gem chance of casting on being hit.
Once triggered, affected skill has a 50% chance +1 per quality of being cast on being hit for 10 seconds, but falls on cooldown for 1 minute.
When on cooldown, the spell cannot be activated.

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So generally positive, then? Cool.

I like your idea of orbs affecting the skillgems, but I am not sure it would work well with the current system. I however think it is a good idea to have skills trigger

on being hit
on block
on death ( for PVP )

listed from less powerfull to more powerfull effects, and also by % chance of occurence

On death should trigger (around) 80%, on block %40, on hit %20

on BEING hit please

I think it should have no mana cost. You dont want too see that all ur mana just dissapear as soon as someone is hitting you. Therefore I think it has to be balanced in other ways.