Hearthpwn

This could be solid with combos and maybe even just clearing boards. This is essentially 'free' with something else in one turn. For example, Turn 5 this into Starfall.

Does the (2) mana spell discount stack when used with Solar Eclipse?

No, Solar Eclipse would require the echo keyword for that, and even then, i don't think it would be discounted. Someone on here probably knows better than I do though.

I think they don't. The wording on Solar Eclipse says that the next spell cast twice so Lunar eclipse would cast the first time and discount the next spell. But then you cast it again so the discount goes away and then apply again. otherwise that would be broken af.

Actually hearthstone very clearly has a distinction between YOU casting spells and spells being cast from other sources, such as minions and spells. For example, spells cast by minions are considered to be cast BY that minion, and spells cast by other spells (such as scroll of wonders or yogg's puzzle box) are cast BY that spell, so it really depends on if YOU have to cast the spell to "use up" the discount.