diff --git a/doc/fixes35.0 b/doc/fixes35.0
index c385d5aa7..2b2d7914e 100644
--- a/doc/fixes35.0
+++ b/doc/fixes35.0
@@ -275,6 +275,7 @@ secret door detection's trap finding is no longer blocked by water or clouds
 	on the Planes of Water and Air
 potion thrown by monster which hit a long worm's tail gave feedback about
 	hitting its head
+implement energy vortex's previously unused energy drain attack
 
 
 Platform- and/or Interface-Specific Fixes
diff --git a/include/extern.h b/include/extern.h
index 5ae8f2eda..b83e45fb2 100644
--- a/include/extern.h
+++ b/include/extern.h
@@ -1099,6 +1099,7 @@ E int FDECL(mdisplacem, (struct monst *,struct monst *,BOOLEAN_P));
 E void FDECL(paralyze_monst, (struct monst *,int));
 E int FDECL(sleep_monst, (struct monst *,int,int));
 E void FDECL(slept_monst, (struct monst *));
+E void FDECL(xdrainenergym, (struct monst *,BOOLEAN_P));
 E long FDECL(attk_protection, (int));
 
 /* ### mhitu.c ### */
diff --git a/src/mhitm.c b/src/mhitm.c
index 31ae58c25..860859966 100644
--- a/src/mhitm.c
+++ b/src/mhitm.c
@@ -1,4 +1,4 @@
-/*	SCCS Id: @(#)mhitm.c	3.5	2007/04/02	*/
+/*	SCCS Id: @(#)mhitm.c	3.5	2007/12/19	*/
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -1121,6 +1121,11 @@ mdamagem(magr, mdef, mattk)
 		}
 		tmp = 0;
 		break;
+	    case AD_DREN:
+		if (!cancelled && !rn2(4))
+		    xdrainenergym(mdef, vis && mattk->aatyp != AT_ENGL);
+		tmp = 0;
+		break;
 	    case AD_DRST:
 	    case AD_DRDX:
 	    case AD_DRCO:
@@ -1449,6 +1454,19 @@ int mdead;
 	return (mdead | mhit);
 }
 
+/* hero or monster has successfully hit target mon with drain energy attack */
+void
+xdrainenergym(mon, givemsg)
+struct monst *mon;
+boolean givemsg;
+{
+    if (mon->mspec_used < 20 &&		/* limit draining */
+	  (attacktype(mon->data, AT_MAGC) || attacktype(mon->data, AT_BREA))) {
+	mon->mspec_used += d(2, 2);
+	if (givemsg) pline("%s seems lethargic.", Monnam(mon));
+    }
+}
+
 /* "aggressive defense"; what type of armor prevents specified attack
    from touching its target? */
 long
diff --git a/src/mhitu.c b/src/mhitu.c
index 141eecee4..9b38755de 100644
--- a/src/mhitu.c
+++ b/src/mhitu.c
@@ -1,4 +1,4 @@
-/*	SCCS Id: @(#)mhitu.c	3.5	2007/06/02	*/
+/*	SCCS Id: @(#)mhitu.c	3.5	2007/12/19	*/
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -1802,6 +1802,12 @@ gulpmu(mtmp, mattk)	/* monster swallows you, or damage if u.uswallow */
 		case AD_DISE:
 		    if (!diseasemu(mtmp->data)) tmp = 0;
 		    break;
+		case AD_DREN:
+		    /* AC magic cancellation doesn't help when engulfed */
+		    if (!mtmp->mcan && rn2(4))
+			drain_en(tmp);
+		    tmp = 0;
+		    break;
 		default:
 		    physical_damage = TRUE;
 		    tmp = 0;
diff --git a/src/monst.c b/src/monst.c
index 0e7bef1fe..b42cdbec5 100644
--- a/src/monst.c
+++ b/src/monst.c
@@ -1,4 +1,4 @@
-/*	SCCS Id: @(#)monst.c	3.5	2007/04/02	*/
+/*	SCCS Id: @(#)monst.c	3.5	2007/12/19	*/
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -955,7 +955,7 @@ NEARDATA struct permonst mons[] = {
 	M2_HOSTILE|M2_NEUTER, M3_INFRAVISIBLE, CLR_CYAN),
     MON("energy vortex", S_VORTEX,
 	LVL(6, 20, 2, 30, 0), (G_GENO|G_NOCORPSE|1),
-	A(ATTK(AT_ENGL, AD_ELEC, 1, 6), ATTK(AT_ENGL, AD_DREN, 0, 0),
+	A(ATTK(AT_ENGL, AD_ELEC, 1, 6), ATTK(AT_ENGL, AD_DREN, 4, 6),
 	  ATTK(AT_NONE, AD_ELEC, 0, 4), NO_ATTK, NO_ATTK, NO_ATTK),
 	SIZ(0, 0, MS_SILENT, MZ_HUGE),
 	MR_ELEC|MR_SLEEP|MR_DISINT|MR_POISON|MR_STONE, 0,
diff --git a/src/trap.c b/src/trap.c
index e22f15a32..a366d8989 100644
--- a/src/trap.c
+++ b/src/trap.c
@@ -1,4 +1,4 @@
-/*	SCCS Id: @(#)trap.c	3.5	2007/08/24	*/
+/*	SCCS Id: @(#)trap.c	3.5	2007/12/19	*/
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -3389,9 +3389,14 @@ drain_en(n)
 register int n;
 {
     if (!u.uenmax) {
+	/* energy is completely gone */
 	You_feel("momentarily lethargic.");
     } else {
-	You_feel("your magical energy drain away!");
+	/* throttle further loss a bit when there's not much left to lose */
+	if (n > u.uenmax || n > u.ulevel) n = rnd(n);
+
+	You_feel("your magical energy drain away%c",
+		 (n > u.uen) ? '!' : '.');
 	u.uen -= n;
 	if(u.uen < 0)  {
 		u.uenmax -= rnd(-u.uen);
diff --git a/src/uhitm.c b/src/uhitm.c
index e969e1a81..1bcab9479 100644
--- a/src/uhitm.c
+++ b/src/uhitm.c
@@ -1,4 +1,4 @@
-/*	SCCS Id: @(#)uhitm.c	3.5	2007/05/16	*/
+/*	SCCS Id: @(#)uhitm.c	3.5	2007/12/19	*/
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -1566,6 +1566,11 @@ register struct attack *mattk;
 		hurtmarmor(mdef, AD_DCAY);
 		tmp = 0;
 		break;
+	    case AD_DREN:
+		if (!negated && !rn2(4))
+		    xdrainenergym(mdef, TRUE);
+		tmp = 0;
+		break;
 	    case AD_DRST:
 	    case AD_DRDX:
 	    case AD_DRCO:
@@ -1958,6 +1963,11 @@ register struct attack *mattk;
 			    golemeffects(mdef,(int)mattk->adtyp,dam);
 			} else dam = 0;
 			break;
+		    case AD_DREN:
+			if (!rn2(4))
+			    xdrainenergym(mdef, TRUE);
+			dam = 0;
+			break;
 		}
 		end_engulf();
 		if ((mdef->mhp -= dam) <= 0) {