It could be used as a shield, easily, have a unit create a shield, and that unit protects all other units until the shielding unit takes too much damage.
This could maybe be used as an effect/emanation, here is effect protection:
Note: If a unit were to protect itself, it would simply take its own damage and/or effects as normal.
Type="effects" means that only effects are absorbed, this could be set to "emanations" or to "all" instead.
<emanations>
<emanation name="effect_protection" bias="beneficial" stacking="overwrite" duration="5" target="ally" radius="16">
<affects>
<...affected units here/>
</affects>
<flags>
<absorbs-detrimental-effects type="effects"/>
</flags>
</emanation>
</emanations>
This would absorb health:
Absorbs-damage value is a percentage that is absorbed, in this case 1.0 is all damage, but weaker units could maybe offer something like 25% protection, var allows for variation just like attack damage or health stealing through attacks and type allows what kinda of damage to be specified (damage multipliers) all would mean all kinda of damage is absorbed. Damage='true' means the protecting units takes all the damage it is absorbing, this could be the default but if set to false, this unit does not take the damage it absorbs and thus you can have a unit that creates a large shield that protects all units from damage until the shielding unit is destroyed.
<emanations>
<emanation name="health_protection" bias="beneficial" stacking="overwrite" duration="5" target="ally" radius="16">
<affects>
<...affected units here/>
</affects>
<flags>
<absorbs-damage value="100" var="0" type="all" damaged='true'/>
</flags>
</emanation>
</emanations>
This could be used to absorb beneficial effects from opponents and becomes the opposite of protection:
<emanations>
<emanation name="effect_steal" bias="detrimental" stacking="overwrite" duration="5" target="foe" radius="16">
<affects>
<...affected units here/>
</affects>
<flags>
<absorbs-beneficial-effects type="both"/>
</flags>
</emanation>
</emanations>
Maybe <absorbs-damage value="-50" var="10" type="all"/> would mean that all damage taken by a unit is shared to other units instead, so with a negative value it does the opposite, this could have some very interesting uses.