Question about Sacrificing and attack phase

[Onetrickpony]

Hello! I some questions regarding some cards in my brothers deck.

Example:
He would declare these attackers:
2x Death Cultist
2x BloodThrone Vampire
1x Emrakul's Hatcher
3x Eldrazi Spawn 0/1 creature tokens

1x raid bombardment

So the first thing that happens is that I take 7 Damage from Raid Bombardment.
Then I assign blockers. Due to trying to defend myself earlier in the game so I wont get killed by Raid Bombardment, I only got one creature to block with.
Naturally I declare to block one of his BloodThrone Vampires.
Then he would sacrifice the 2 Death Cultists, 3 Eldrazi Spawn tokens.
So my blocker dies, cus the blocked and unblocked vampires becomes 11/11
Then i take 2 damage from the death cultists he sacrificed(he gains 2 life)
Plus 3 damaged from Emrakul's Hatcher
So in total I would loose a whooping 23 Life to an attack 6 rounds into the game.

Hes maxed his Death Cultist, Bloodthrone Vampire and Raid Bombardment count in his deck, so this scenario is due to happen at least 3/5 games.

My question is, can he really sacrifice creatures so freely during the attacking phase? And can he benefit from the Raid Bombardment when he sacrifice half of his attackers and the other half get buffed above 2 in power? Its very frustrating :(

[Seras]

the way he's playing it is correct except in one detail:

the raid bombardment effect does triggers when he declares the attackers, you take the damage immediately, before the next step of combat.

bloodthrone vampire's ability does works at instant speed so he can activate that as a response to you declaring your blockers.

(since sacrificing the creature it actually the cost of the ability, you can't counter it in any way, it happens when you put the ability on the stack, not when it resolves.)

However, the death cultist can either be sacrificed to pay for their own ability or the vamp's, but not both. in both cases the sacrifice is a cost, not a trigger(like the mortician beetle, for example).

same goes for the spawns, if he sacs them for the vampire he doesn't get the colorless mana.

[Onetrickpony]

Thanks alot, cleared some things up :) Tho one last question; if you got 2 Bloodthrone Vampire on the battlefield. Then you sacrifice one Death Cultist for the vamp's ability, will both of the vamp's get +2\+2 ?

[Seras]

no, you sacrifice one creature to pay for and activate one of the vamp's ability.

[Onetrickpony]

Cool, Thanks again! Time to swing my nerf hammer :)