So I just got a crash in the Halloween event as follows:
- My opponent had a Relentless Dead out, a zombie tokens stack, and a Graf Harvest out.
- I cast a Plague Wind to remove their board and punish them for a rather generous zombie stack.
- Plague Wind fired off and started removing the board and dealing damage all at once.
- When Relentless Dead was destroyed, it came back to the battlefield and it appeared in the regular popup.
- Due to Graf Harvest triggering on the Dead dying, it also triggered a zombie creature popping back to the battlefield that caused another popup.
- The zombie token popup closed itself after its regular period.
- The Relentless Dead popup remained on the screen.
My suspicion here is related to Plague Wind behavior rather than anything else. Let me explain why I think it is so:
- Plague Wind is very weirdly implemented. It triggers destroying everything at once as well as dealing damage at the same time (when compared to Hour of Devastation for example that seems to remove the creatures one by one)
- Because the two creatures are destroyed in parallel, each triggers a chain of actions in parallel - the relentless dead comes back and triggers a Graf Harvest zombie afterwards, while killing the zombie stack triggered a Graf Harvest zombie of its own
- Because two popups appeared at the same time, the system somehow must keep track of the last → hence the Relentless Dead popup remains stuck in limbo somehow as the system only removes the last one
Once again, this seems to be the kind of bug that would be fixed by a proper implementation of all cards that deal with multiple objects on the board (and/or other supplementary actions). In paper magic all these actions happen at the same time, and any effects associated with them are put onto the stack before resolving ONE BY ONE. In MTGPQ, some cards behave like this while others just go crazy (I once finished a game with Plague Wind dealing fatal damage, and animations still seemed to be flying around behind the scenes in the score screen).
My recommendation would be to properly implement the stack behind the scenes, let a card’s effect fully resolve, and then start resolving the resulting effects one at a time. For simultaneous effects I would also have no problem if the order they are put on the stack is actually in queue order (FIFO), since in paper magic it is the player who owns the abilities that gets to put them on the stack in whatever order they wish. The main issue here is that there are no clear rules as to when effects happen in “parallel”, when they happen sequentially and there seems to be no uniform engine/structure for different cards!