This might be the same underlying issue but there's a /marvel-snap.rss linked from it too which doesn't appear to have a corresponding route (it renders the normal index page).

HS_Alec confirmed on Reddit that Spellburst only happens after the spell resolves, so he would have to survive. (https://www.reddit.com/r/hearthstone/comments/hvjzcx/new_card_reveal_headmaster_kelthuzad_the_first/fytv8lu/)