What verb is かまされる?

Question

In the first light novel of the Konsuba series there are two pages of character profiles. In them Kazuma say to Darkness,

どこかの誰かに爆裂魔法をかまされたからな

I am confused as to the meaning and identifying what verb that is. Any ideas?

Answer 1

かます is a slang that can replace almost any transitive verb to make it sound aggressive and/or vulgar, but with no clear meaning in itself. You can translate it using a sort of easy formula such as "give (somebody) a hell of —", but I think there will be indefinite ways of translation according to the actual situation.

はったりをかける make a bluff → はったりをかます make a big fat bluff

ボケを言う tell a joke → ボケをかます crack a joke

ラップを歌う do a rap (lit. "sing") → ラップをかます bust a rap

Since かます stands in place of the original verb, we can't know what word were originally there without context. The most straightforward reading here is that the magic hit Kazuma in a manner causing some injury, in this case:

Just because someone set a fuckin' explosion magic on me.

However, there is also a possibility that Darkness otherwise made a blunder on magic and Kazuma suffered from it (e.g. loss, blame, etc.) → indirect passive

Note that どこかの誰か is a fixed phrase sarcastically refers to "you" or "who we obviously know", as much as one of usage of English someone.

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Though this slang is technically a definition under 噛ます "force into; wedge into", its accent is usually realized かます{LHH} nowadays where the non-slang accent is かます{LHL}, which is the regular derivation from かむ{HL} (噛む).

Answer 2

Probably it is the passive form of 噛{か}ます・嚙{か}ます in コトバンク.

It explains

「食{くら}わせる」に同じ。 「突っ張りを－・す」 「一発－・す」

Unleash a slap to the opponent.

Give the opponents one shot.

Also, the entry of 食{くら}わせる in コトバンク.

人に攻撃を与える。こうむらせる。 「びんたを－・せる」 「肘鉄砲を－・せる」

Jolt the opponents with one's elbow/slap.

I think 爆裂魔法をかまされた is something alike.

So, my image is someone suddenly shot/splashed/thrust tremendous magic to the Darkness from somewhere.