Dies to Removal

Ah. Missed the "until" part. Clever, Wotc, clever. My mistake.

I dont really get why you are so ezcited with brain magot. I will say it again. How do you even have spot for this creature and what are ypu cutting for it? Most of the time you are forced to take removal as they could just kill magot to get the other card back. It isnt tidehollow sculler, which has 2 power and an exile a card complete,ly.

You are saying you take removal so they cant target your pain seer. When do you even cast your pain seer then? Remember you can still kill in response so you dont even look in my hand(I think. Similar as killijg banisher priest
targeting token in response).

Trigger still resolves, so you look at the hand. The card you choose to take simply goes back to the player's hand immediately.

This is incorrect. If someone is dumb enough to toss a removal spell at the maggot in response to the ETB trigger, here's the stack.

Remove card from hand
Removal

After the creature dies.

Remove card from hand
Return the card to hand

So, the card, which hasn't been chosen yet, is "returned". Now they resolve the exile effect and the card is permenantly gone. It's the old fiend hunter trick. So, in other words, if your opponent only has one removal in hand, he's screwed as you can just take it from him or he can kill your dinky 1/1 and get "thoughtsiezed".