Had an interesting thing happen.
Was fighting against a PVP match that included Death. He cast which deathmarked my entire team. On my turn nobody died and I got my gorgotha to full mana planning to cleanse it next turn. AI takes a turn and I click on Gorgotha as soon as my turn starts. The cast screen comes up, but his portrait is already black from deathmark going off. I click cast anyway and the explosions fire, but as the deathmark had already killed him the troop was still dead.
Classic race condition, allowing me to click a troop before “start of turn” events complete, much like how an Empowered troop can cast before traits are finished.