Energy Shield

Diablo II	Notation	Basic	Class	Skill	Item	Ally	Quest	Area	Monster	Tale

1
2

Charged Bolt
Static Field

3
4

Telekinesis
Nova

5
6

Lightning
Chain Lightning

7
8

Teleport
Thunder Storm

9
10

Energy Shield
Lightning Mastery

Type	Personal defensive buff
Tier	5
Required level	24
Required skills	Chain Lightning, Teleport
Requirements	None
Left button	No
In town	Yes
Mana cost	5
Attack no mana	No
Weapon damage	No
Synergy skills	Telekinesis

Level01
6
12
18
24
30

Sheathing herself in pure energy, the Sorceress walks fearlessly into the fray. So long as she can maintain her concentration over this magical buffer, she diverts harmful magical energies and absorbs physical harm into her store of Mana.

Detail

Stat	Value
% Damage Absorbed to Mana	100 * ( (32-Telekinesis.blvl) / 16)
Duration (Seconds)	84 +(60*slvl)

Stat	Level
Stat	1-8	9-16	17-22	23-28	>28
% Damage Absorbed	15 + (5*slvl)	39 + (2*slvl)	55 + slvl	55 + slvl	min(55+slvl , 95)

Overlay above head when active.

Energy Shield in action.

Absorbs damage after Bone Armor and Cyclone Armor are applied. [1]
Absorbs physical damage, Magic Damage, Fire Damage, Lightning Damage, Cold Damage, stamina damage and mana damage, but not Poison Damage (not even the first frame). [2]
Applies to damage returned by Thorns, Iron Maiden and Spirit of Barbs, and to Static Field damage. [3] [4]
Does not apply to Sacrifice self-harm, Open Wounds or Crushing Blow. [5] [6]
Level >39 absorbs 95% damage.
200% of damage absorbed is redirected to mana unless skill points are invested in Telekinesis:

Stat	Level
Stat	1	2	3	4	5	6	7	8	9	10
% Redirected to Mana	193.75	187.5	181.25	175	168.75	162.5	156.25	150	143.75	137.5

Stat	Level
Stat	11	12	13	14	15	16	17	18	19	20
% Redirected to Mana	131.25	125	118.75	112.5	106.25	100	93.75	87.5	81.25	75

Level 20 Energy Shield absorbs 75% damage: this would result in 100 damage being reduced to 25. With no points in Telekinesis 200% of 75 is redirected to mana, so 25 life and 150 mana is lost instead of 100 life; with 20 points in Telekinesis, only 75% of 75 is redirected to mana, so 25 life and 56.25 mana is lost instead of 100 life. Equipping (Magic) Damage Reduced by 25 would then result in no life loss.
100 base mana damage would normally be increased to 200 in Hell after the Resist -100% penalty. However, level 20 ES and level 20 Telekinesis reduce base mana damage to 25 (which is subsequently increased to 50 in Hell) then 75% of 75 is redirected to mana, resulting in just 106.25 (50+56.25) mana lost instead of 200 mana (ES mana loss is applied before final mana damage). [7]
Expires when its duration expires, or when the Sorceress is reduced to zero mana.
When redirected damage > mana, then remaining mana absorbs equivalent damage and remainder is applied to life. 100 damage applied to level 40 ES (95%) with level 20 Telekinesis (0.75) normally results in -5 life and -71.25 mana; however, if only 60 mana remains then that only absorbs 80 (60/0.75) damage, resulting in -20 life and zero mana.
When there is sufficient mana to absorb redirected damage but mana damage subsequently results in 0 mana, redirected damage is absorbed in full beforehand.
Redirecting damage from life to mana can be preferable due to its innate regeneration, which can be increased significantly by Regenerate Mana +% from Warmth, Meditation and items.
Mana damage from Wraiths, Willowisps and Mana Burn Unique monsters (and their minions in Nightmare and Hell) can be significant enough to make it difficult to maintain ES. In D2&LoD, melee attacks of Mana Burn Unique monsters and their minions apply mana damage 256 times higher than they should: this can be enough to reduce a Sorceress from full to zero mana with a single hit. [8] This has been fixed in D2R.

Damage Taken Goes to Mana

% Damage Taken Goes to Mana returns mana after Energy Shield's mana loss: ES expires when more mana is lost than the Sorceress currently has, even if DTGM fully compensates for it afterwards. [9]
DTGM can counter ES mana loss when damage is from applicable source and the loss does not result in no mana. In the absence of any later damage reduction, percentage DTGM (M) required to balance mana loss for any given ES percentage (E) and Telekinesis level (T) is as follows:

M = { 100E (2 - 0.0625T) / (100 - E) }

Table below lists DTGM percentages required to counter ES mana loss from applicable damage for all combinations of ES and Telekinesis level: maximum 342% DTGM can be equipped by a Sorceress in an unmodified game. [10] Balance may still be achieved for values highlighted in orange when Resist < 0%. Actual percentage can be multiplied by (100-Resist)/100 to achieve virtual percentage: 342% becomes 684% for Resist -100% (final damage is doubled so percentage required is halved). Balance can never be achieved for values highlighted in red in an unmodified game, even for Resist -100%.

Energy Shield		Telekinesis Level
Level	%	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20
1	20	49	47	46	44	43	41	40	38	36	35	33	32	30	29	27	25	24	22	21	19
2	25	65	63	61	59	57	55	53	50	48	46	44	42	40	38	36	34	32	30	28	25
3	30	84	81	78	75	73	70	67	65	62	59	57	54	51	49	46	43	41	38	35	33
4	35	105	101	98	95	91	88	85	81	78	75	71	68	64	61	58	54	51	48	44	41
5	40	130	125	121	117	113	109	105	100	96	92	88	84	80	75	71	67	63	59	55	50
6	45	159	154	149	144	139	133	128	123	118	113	108	103	98	93	87	82	77	72	67	62
7	50	194	188	182	175	169	163	157	150	144	138	132	125	119	113	107	100	94	88	82	75
8	55	237	230	222	214	207	199	191	184	176	169	161	153	146	138	130	123	115	107	100	92
9	57	257	249	241	232	224	216	208	199	191	183	174	166	158	150	141	133	125	116	108	100
10	59	279	270	261	252	243	234	225	216	207	198	189	180	171	162	153	144	135	126	117	108
11	61	304	294	284	274	264	255	245	235	225	216	206	196	186	176	167	157	147	137	128	118
12	63	330	320	309	298	288	277	267	256	245	235	224	213	203	192	181	171	160	149	139	128
13	65	360	349	337	325	314	302	291	279	267	256	244	233	221	209	198	186	175	163	151	140
14	67	394	381	368	356	343	330	318	305	292	280	267	254	242	229	216	204	191	178	165	153
15	69	432	418	404	390	376	362	348	334	320	307	293	279	265	251	237	223	209	195	181	167
16	71	475	460	444	429	414	398	383	368	352	337	322	307	291	276	261	245	230	215	199	184
17	72	499	483	467	450	434	418	402	386	370	354	338	322	306	290	274	258	242	225	209	193
18	73	524	507	491	474	457	440	423	406	389	372	355	338	322	305	288	271	254	237	220	203
19	74	552	534	516	499	481	463	445	427	410	392	374	356	338	321	303	285	267	250	232	214
20	75	582	563	544	525	507	488	469	450	432	413	394	375	357	338	319	300	282	263	244	225
21	76	614	594	574	555	535	515	495	475	456	436	416	396	377	357	337	317	297	278	258	238
22	77	649	628	607	586	565	545	524	503	482	461	440	419	398	377	356	335	314	293	273	252
23	78	687	665	643	621	599	577	554	532	510	488	466	444	422	399	377	355	333	311	289	266
24	79	729	706	682	659	635	612	588	565	541	518	494	471	447	424	400	377	353	330	306	283
25	80	775	750	725	700	675	650	625	600	575	550	525	500	475	450	425	400	375	350	325	300
26	81	826	800	773	747	720	693	667	640	613	587	560	533	507	480	453	427	400	374	347	320
27	82	883	855	826	798	769	741	712	684	655	627	598	570	541	513	485	456	428	399	371	342
28	83	946	916	885	855	824	794	763	733	702	672	641	611	580	550	519	489	458	428	397	367
29	84	1,018	985	952	919	886	854	821	788	755	722	690	657	624	591	558	525	493	460	427	394
30	85	1,098	1,063	1,028	992	957	921	886	850	815	780	744	709	673	638	603	567	532	496	461	425
31	86	1,191	1,152	1,114	1,075	1,037	999	960	922	884	845	807	768	730	692	653	615	576	538	500	461
32	87	1,297	1,255	1,213	1,172	1,130	1,088	1,046	1,004	963	921	879	837	795	753	712	670	628	586	544	502
33	88	1,421	1,375	1,330	1,284	1,238	1,192	1,146	1,100	1,055	1,009	963	917	871	825	780	734	688	642	596	550
34	89	1,568	1,518	1,467	1,416	1,366	1,315	1,265	1,214	1,164	1,113	1,062	1,012	961	911	860	810	759	708	658	607
35	90	1,744	1,688	1,632	1,575	1,519	1,463	1,407	1,350	1,294	1,238	1,182	1,125	1,069	1,013	957	900	844	788	732	675
36	91	1,960	1,896	1,833	1,770	1,707	1,644	1,580	1,517	1,454	1,391	1,328	1,264	1,201	1,138	1,075	1,012	948	885	822	759
37	92	2,229	2,157	2,085	2,013	1,941	1,869	1,797	1,725	1,654	1,582	1,510	1,438	1,366	1,294	1,222	1,150	1,079	1,007	935	863
38	93	2,575	2,492	2,409	2,325	2,242	2,159	2,076	1,993	1,910	1,827	1,744	1,661	1,578	1,495	1,412	1,329	1,246	1,163	1,080	997
39	94	3,036	2,938	2,840	2,742	2,644	2,546	2,448	2,350	2,253	2,155	2,057	1,959	1,861	1,763	1,665	1,567	1,469	1,371	1,273	1,175
40	95	3,682	3,563	3,444	3,325	3,207	3,088	2,969	2,850	2,732	2,613	2,494	2,375	2,257	2,138	2,019	1,900	1,782	1,663	1,544	1,425

(Magic) Damage Reduced, resistance and absorb can reduce damage applied and thus increase percentage required to counter ES mana loss: Resist 50% will double percentage required, Resist 75% will quadruple it. [11]

Source

Skill bonus

+(1-3) Energy Shield (Sorceress Only) can spawn on ilvl >24 orbs and staves.

Value	Source	Min Rlvl	Ladder
+3	Memory staff	37	No
+3	Warpspear Gothic Staff	39	No
+3	Ormus' Robes Dusk Shroud	75	No

Levels 1-60

Stat	Level
Stat	1	2	3	4	5	6	7	8	9	10
% Damage Absorbed	20	25	30	35	40	45	50	55	57	59
Duration (Seconds)	144	204	264	324	384	444	504	564	624	684

Stat	Level
Stat	11	12	13	14	15	16	17	18	19	20
% Damage Absorbed	61	63	65	67	69	71	72	73	74	75
Duration (Seconds)	744	804	864	924	984	1,044	1,104	1,164	1,224	1,284

Stat	Level
Stat	21	22	23	24	25	26	27	28	29	30
% Damage Absorbed	76	77	78	79	80	81	82	83	84	85
Duration (Seconds)	1,344	1,404	1,464	1,524	1,584	1,644	1,704	1,764	1,824	1,884

Stat	Level
Stat	31	32	33	34	35	36	37	38	39	40
% Damage Absorbed	86	87	88	89	90	91	92	93	94	95
Duration (Seconds)	1,944	2,004	2,064	2,124	2,184	2,244	2,304	2,364	2,424	2,484

Stat	Level
Stat	41	42	43	44	45	46	47	48	49	50
Duration (Seconds)	2,544	2,604	2,664	2,724	2,784	2,844	2,904	2,964	3,024	3,084

Stat	Level
Stat	51	52	53	54	55	56	57	58	59	60
Duration (Seconds)	3,144	3,204	3,264	3,324	3,384	3,444	3,504	3,564	3,624	3,684

Reference

Lightning Spells (Arreat Summit)
Energy Shield, Damage Taken Goes To Mana, Mana Burn (D2 Technical)
Nefarius, v1.10-v1.11b Bugs Collection (Phrozen Keep)
SSoG, Damage Goes To Mana + Energy Shield (D2 Sorceress)