Revamp shock serpents

While the original version may have been conceptually interesting, it
had multiple mechanical problems. Even putting aside the bugs in the
implementation of monster static discharge, frying its allies when
injured doesn't seem like a good mechanic to me, and the way static
discharge jumps means that many messages are generated for every single
event (for similar reasons I don't think it works very well as an active
spell for them either). Also, shock's damage scaling meant it was
basically harmless on a monster of this tier - a cantrip as best.

This commit attempts to take the central concepts of the original
design and make it a more effective and workable monster. Shock
serpents now passively gather charge when in combat. After multiple
turns of building charge, they can unleash it as an unavoidable arc
of lightning aimed at their primary target (and nearby allies, in the
style of dazzling spray) which does substancial damage. However,
injuring the shock serpent discharges ALL of the sustained charge
as a (much weaker) reprisal effect. The idea is that the player will
be encouraged to suffer through the reprisal to avoid a worse attack
and that it might sometimes change target priorities in a large melee
or affect retreat tactics employed.

In addition, I have replaced shock with a stronger electrical bolt
styled after electric eels. The code duplication involved here bugs
me, but shocks if far too weak and lightning bolt too strong and the
electric eel bolt cannot just be made into a spell and given to both
of them without reducing eel fire rate significantly.

Finally, they get slight hd and melee boost, and lose the poison
resistant and poisonous corpses. So much of Snake already leaves
poison corpses and it doesn't seem to me that there's much need for
any poison association here.

Note that a great many numbers here are quite provisional, particularly
charge rate and the power of lightning torrent itself.

1 files changed, 1 insertions, 0 deletions

diff --git a/crawl-ref/source/mon-abil.h b/crawl-ref/source/mon-abil.h
index 0471a07406..105f6ff5b2 100644
--- a/crawl-ref/source/mon-abil.h
+++ b/crawl-ref/source/mon-abil.h
@@ -46,5 +46,6 @@ bool apply_grasping_roots(monster* mons);
 void check_grasping_roots(actor* act, bool quiet = false);
 
 void siren_song(monster* mons);
+void shock_serpent_discharge(monster* serpent);
 
 #endif