The game sees that you're supposed to lose while checking the state-based effects. (Or is it state-based actions? They switched and I forget which way that switch went. Anyway...)

Life and Limb and Blood Moon is better, but Hallow plus Hostility in a multiplayer game can be ridiculous depending on the spell.

Overall, most of the true corner-case stuff takes three or more cards to pull off--Clone/Mimic Vat/Doubling Season's been a favorite of mine recently.

What is the interaction between Hostility and Hallow? Isn't only one of them going to end up applying in a given case?

For the clone/vat/season, each token can copy something different, right?

And I think there used to be a question of how something like Biomantic Mastery would interact with a Seht's Tiger, but I don't remember how it worked out.

so I could be wrong, but eyeballing it, in a multiplayer game with something like sizzle, I think each player gets to choose individually whether hallow's controller gains life or hostility's controller gets tokens, since each of them is the affected player for the damage dealt to them. maybe there's more to it, I don't know, but that's the first thing that stands out to me.

Basically, the Tiger accomplishes absolutely nothing. (Except increasing that player's creature count by 1, for more cards drawn.)

The spell or ability is countered if all its targets, for every instance of the word “target,” are now illegal. If the spell or ability is not countered, it will resolve normally. However, if any of its targets are illegal, the part of the spell or ability’s effect for which it is an illegal target can’t perform any actions on that target, make another object or player perform any actions on that target, or make that target perform any actions. If the spell or ability creates a continuous effect that affects game rules (see rule 613.10), that effect doesn’t apply to illegal targets. The effect may still determine information about illegal targets, though, and other parts of the effect for which those targets are not illegal may still affect them.

We need more fun rules discussions on this forum. I miss going to the Mothership Rules Q&A section and answering quick questions to get my rules fix.

Nope. Currently, the rules for replacement effects are set up such that they have to be a copy of the same thing. Which everybody gets wrong.