can something like execute be cast if there's no white creatures in play?
No. You can't cast a targeted spell if there are no legal targets for it.
seen from China
seen from Russia

seen from Bolivia

seen from Israel
seen from Netherlands
seen from Israel
seen from China
seen from Jordan
seen from Russia

seen from Libya
seen from Türkiye
seen from Ukraine
seen from Netherlands
seen from United States
seen from United Kingdom
seen from Türkiye

seen from United States
seen from United Kingdom

seen from Kazakhstan

seen from United States
can something like execute be cast if there's no white creatures in play?
No. You can't cast a targeted spell if there are no legal targets for it.
is burnt offering legal in mono-black commander?
No.
It has {R} in its oracle text, which makes its color identity red and black.
I put treacherous link onto my own palisade giant, someone casts some burn at me, who takes damage?
You do.
First, Palisade Giant redirects the damage to itself, then Treacherous Link redirects the damage to you. (Palisade Giant can't try to redirect it again, because it's already applied its effect to the damage once.)
how does totem armor interact with bestow? say my umbra mystic has hopeful eidolon bestowed onto it, and someone targets it with a doom blade, what dies?
The aura is destroyed instead of the creature its on. Eidolon bites it.
if there's a garruk's packleader and worldspine wurm in play and the wurm dies, what's the order of events for shuffling the wurm, getting the tokens, and drawing from the packleader?
Both of Worldspine Wurm's triggers will go on the stack at the same time and resolve in whatever order you want. Once the tokens arrive, the Packleader will trigger and draw you some cards, so this could be either before or after the Wurm gets reshuffled into the deck.
In multiplayer, if an opponent targeted with Nyxathid loses the game, does Nyxathid need to target another opponent or will the minuses stop happening?
You don't choose another player, Nyxathid just stays as a 7/7.
as to why Gadreel would have wanted to posess Sam. Well, this is his first time on earth in millenia, he has no idea the current state of things and it's doubtful that he knows all of the Winchester Going-ons. But Dean knew what he was doing saying a prayer, having holy oil on hand, having an angel blade ready to fight. I can't remember if there was indication that he recognized Winchester, but he could recognize preparedness for what's going on, knowledge, and a vessel that wouldn't break.
The thing is....it might be something like that, but I just feel like it has to be something more. The mythology associated with Gadreel could tie into so many things already in the spn-verse (Nephilim, human/angel love, Azazel, Cain, Abaddon)...there is literally so much potential there. It may never be addressed, but I really hope it is, because it would be the biggest wasted opportunity ever imo. :3
typefourtytardiss replied to your text post
it's better interpreted as "I did what I felt I had to do" which is less significant to say, more wordy, and has little amount of difference in the situations. they are all taking responsibility for their actions.
Oh I didn't think of it like that!
So you think their use of the phrase was them all admitting and taking responsibility?
Ah. Yes, okay, that's certainly possible! Good point. That certainly seemed how CAS seemed to be saying it, actually - he acknowledged he'd MADE himself a 'barbarian'...
...but idk with Dean and Gadreel and the other angel. I think it can just as much be read as them trying to AVOID taking responsibility for their actions but trying to convince themselves, and others, that they had no other choice, ergo it wasn't their fault or their responsibility.
Ooooh, now there are LAYERS to it! :D