I think the cost should be more.
It adds defense already but quanta too? The differnce between this and Solar shield is the element and the details of the effect. Darkness get's quanta too easy as it is.
Don't get me wrong it is not broken or anything but a small cost increase would be good.
Note that it's random quanta, most of wich will stay unused. While all Solar shields quanta is useable.
Darkness mostly only get's dark quanta easy (Devourers), unless off course a quantum tower is stolen, wich is a waste of the steal spell is most cases.
Well that's all true but some darkness cards use other elements. Most of the time you need to change your mark or play other cards just to use the effects of some darkness cards. It just seems that giving Mono darkness more options like to burrow devourers, give +0/20 to a garg or have a bloodsucker be able to use it's effect without running a mark or any other form of quanta generation seems a little too much for me.
Also it reduces damage in an element where you have vampire's and liquid shadow. This just adds to things.
I mean the upped one cost 3 but has 2 defense and generates quanta in an element that as a mono is already tier 1 in PvP? Also I played mono darkness alot in PvP lately, the last this it needs is a buff.
I am not fully against a buff but this is just too good.