Fall from Favor

If combat damage dealt to the monarch causes that player to lose the game, the triggered ability that causes the controller of the attacking creature to become the monarch doesn't resolve. In most cases, the controller of the attacking creature will still become the monarch as it is likely their turn.

If the triggered ability that causes the monarch to draw a card goes on the stack and a different player becomes the monarch before that ability resolves, the first player will still draw the card.

If the target creature is an illegal target by the time Fall from Favor tries to resolve, it doesn't resolve. It won't enter the battlefield, so its enters-the-battlefield ability won't trigger.