Anyone created a true AOE yet?

Not sure if this is what you are trying to do, but the Explosion ablilty/spell of the Vigilant Minion and one of the creatures from the campaign effects all enemies.  I can't seem to find it right now though.

Regarding damaging all: there is already a spell for that:

  <!-- ************** -->
  <!-- * Arcane Doom* -->
  <!-- ************** -->
  <SpellDef InternalName="ArcaneDoom">
    <DisplayName>Arcane Doom</DisplayName>
    <Description>All enemy units are struck by an arcane explosion and take 10 true damage.</Description>
    <Image>WaterCrystal_Medallion.png</Image>
    <IconFG>Arcane_Doom.png</IconFG>
    <IconColor>32,45,243</IconColor>
    <Range>-1</Range>
    <Radius>30</Radius>
    <SoundFX>Spell_DarkEnchant_01</SoundFX>
    <ManaCost>3.0</ManaCost>
    <SpellLevel>1</SpellLevel>
    <SpellType>Tactical</SpellType>
    <SpellClass>Offensive</SpellClass>
    <SpellTargetType>EnemyUnitIgnoreFriendly</SpellTargetType>
    <IsSpecialAbility>1</IsSpecialAbility>
    <GameModifier InternalName="ArcaneDoomModifier">
      <ModType>Unit</ModType>
      <Attribute>CurHealth</Attribute>
      <Value>-10</Value>
    </GameModifier>
    <SpellDefEffect>
      <EffectName>Arcane_Doom</EffectName>
      <LocalPosition>0,0,0</LocalPosition>
      <EffectScale>0.75</EffectScale>
      <EffectDelay>0.0</EffectDelay>
      <SnapToTerrain>1</SnapToTerrain>
      <PlayOnAllTargets>1</PlayOnAllTargets>
    </SpellDefEffect>
  </SpellDef>

Lifesteal could be implemented as far as I see. Damaging and healing of units is already implemented. One would just have to juggle the Strings around a bit I guess.

Technically, that's just a spell with a large enough radius to cover the entire battlefield.

I'm not sure you can do a lifesteal spell. The modifier doesn't seem to contain information about who it's hitting. Rather, that seems to be determined by <spellclass> or <spelltargettype>. That would make it difficult to do a spell that does one thing on friendlies, and another on hostiles.

This AOE doesn't look any different form other spells that only hit every unit once, making them pointless. (oh, they are good vs. an army of 10 single spiders but...)

I think with "real AOE" he means that every person in every unit should get hit instead of the whole 20 person unit getting hit once for a then trivial amount.

The whole concept of AOE spells is based on every living (well, mobile) thing getting hit. Not 4 person units taking 1/4 of the relative damage and 20 person units taking 1/20...

That would imply that the damage per unit is multiplied by the target unit's member count. Obviously it cannot scale up "as usual" by the number of shards but needs a more timid progression. Like +4 for 4 shards instead of  x 4.

And Lifesteal?  What about the very first spell in  CoreSpells_RUIN_Tactical.xml ?

Sorry, I should have clarified.  I meant a spell that hits all units on the battlefield, both friendly and enemy.  All of the stuff I have played with seems to ignore friendly units by default.  My ultimate goal was to create either a large board-covering aoe that hit both armies indescriminately, or a single target spell that hit an enemy (presumably for 2X damage or something), but also damaged (I tried downmodding constitution for the same effect) the caster for up to his intelligence value.  You know, the kind of risk vs. reward spells that make combat interesting.  My hope was to implement these alongside a group of sovergin-only spells (or abilities) that would give leveling your soverign as your sole mage a purpose. 

Anyway, I'm rambling.  If anybody knows how this might be done I'd appreciate a shout, and thanks for the comments so far.

@Robert you're right! Nice find. Sadly the spell doesn't have two functions, but the attribute is pretty cool: StealUnitStat

@Troggie87 the known values for <SpellTargetType> tag are:

EnemyUnit

FriendlyUnit

NeutralGround

NeutralTerritory (only used by blink, which isn't used in game, so possibly deprecated)

EnemyUnitIgnoreFriendly

Beyond those, you'll have to experiment.

I have not tested all of these. These come from looking for valid tags in the EXE file. Thanks.

Spell Target Types:

EnemyTerritory

EnemyCity

FriendlyCity

NeutralGround

FriendlyTerritory

Self

Monster

EnemyUnitIgnoreFriendly

EnemyUnit

FriendlyChampion

FriendlyUnit

Any (I would test this one with a large radius on the spell).

That looks like what I need, thanks a lot .  Hopefully Stardock will come out with some published notes on this stuff or something, stumbling around like this gets a little tiring.