Screaming Banner first: Attach to a target Undead unit you control. ACTION: When attached unit attacks, target unit loses 2 Power until the end of the turn.

Reading that the DE Spearmen could be 'pumped'. Does this work in the same way? So if the attached unit attacks, essentially I can remove 'all' the power symbols from all defenders? It doesn't say limit once or something similar.

Draing Magic vs. Blood Summong:

BS: Spell: ACTION: Corrupt X units you control to lower the cost of the next Chaos unit you play this turn by X.

DM: Spell: Action: Cancel a spell card just played.

This is really a question about 'paying all costs'. Do you corrupt the wanted units as part of the cost? If I cancel BS with DM, does my opponent still have to corrupt units?

Thx in advance

edderkoppen said:

For SB, attacking is the trigger for the Action, so you can do it just once. Otherwise 1 Descendant of Indraugnir could do X times 4 indirect with a single attack, basically barring toughness one attack would end the game. Naggaroth Spearmen aren't worded in that manner:

"ACTION: Spend X Resources to have this unit deal +X Damage in combat until the end of turn. X is the number of Developments in this Zone."

They can even do it on defense.

edderkoppen said:

Hmm, cost for BS is 0CCC and if it resolves, then your opponent would corrupt X units, but your DM cancels BS before it resolves. Not 100% on this though.

For your second question, corrupting the units is part of the cost of playing the card, just like sacrificing a unit to Whip the Slaves or such. If the latter was canceled, your sacrificed unit would still be gone. So, yes, the units would be corrupted.