Core Tap - help understanding mana costs using 917

[drumpel]

I think I'm brain dead today and I can't math, so any clarification to help me out would be great.

68 ranks EL:W = 82 "free" mana using 950

3 targets, using INCANT 950 917 costs me 50 mana. I cast the spell 3 different times against only 3 targets and it always costs me 50 mana.
1st cast: I had 165 mana, ended with 115
2nd cast: I had 78 mana, ended 28
3rd cast: I had 122 mana, ended with 72

*Update*
I just came across a group of 4 creatures. So I tossed out INCANT 950 917 and it only cost me 50 mana.
I had 122 mana, ended with 72

Can someone break down the math for me? I tried to figure out based on what the gswiki explains, but I'm either reading how to do the math wrong or something isn't working right when using 917 and 950.

[Donquix]

the mana cost is per total spell cast, not per target hit by those spells. AoE spells cast normal since they would already hit all the targets, single target spells cost double and hit every target.

If you're only casting 917 once (1 cast of 917 for every creature in the room, up to your target limit) the total cost is only 34 mana, so you are charged the minimum of 50.


You could cast
512 - aoe so base cost = 12
512 - aoe so case cost = 12
917 - single target x2 = 34
903 - single target x2 = 6
903 - single target x2 = 6
903 - single target x2 = 6

12 + 12 + 34 + 6 + 6 +6 = 76 mana which would still only cost you 50 mana because of the water lore and every creature up to your target limit would be (assuming they fail all wardings) encased in ice, earthen furied, and hit with 3 minor waters, in 1 spell cast for 50 mana.

Core tap is good.

[drumpel]

Thanks for the clarification. I've been running on empty the past few days - things just weren't clicking in my head. I need to just simply crash when I get home and sleep for a good 12 hours.

[drauz]

The spell will always cost at minimum 50 mana.

AoE spells only cost 1x their mana cost (410, 912, etc.)
Single targets spells cost 2x their normal mana cost.

So if you cast:

410 (10 mana), 510 (20 mana), 510 (20 mana), 510 (20 mana), 510 (20 mana), 510 (20 mana)

Add these up then subtract your "free" mana bonus, so :

(10+20+20+20+20+20) - 82 = 28

Then add the minimum cost for the spell back in:

28+50= 78

This spell combo would cost you 78 mana.