i dont understand villein

I can see how this card Is insanely key to any deck but I dont understand the wording. does it always cost one blood to play? why does it read "additional pool to play"? additional to what? also, how does this interact with minion tap and lastly, this is way better than minion tap, right? they do similar things villein just does it ten times better. so in a game where there is no limit to the number of copies you can run, then why would anyone ever run minion tap? hmm.. maybe with weenies, transferring 2 blood can be too much sometimes?

Villein is definitely useful in a wide variety of decks, but it's not always better than Minion Tap.

First, Villein requires you to take at least two blood from the vampire (you can take less if they have less, but must declare that you're taking at least two blood). Minion Tap has no minimum amount than can be taken. Late game cycling of Minion Tap tends to be much easier.

Second, Villein is capped at taking five blood. Minion Tap has no maximum. If you're playing really large vampires, like Lutz, you may want to take more back than the five that Villein will allow.

Third, Villein stays in play on the vampire. It costs you an additional pool per Villein on the target vampire to target a vampire with another Villein. This effectively means that the second Villein costs a pool, meaning the most you will realize from it is a four pool gain. Villein also makes your Minion Taps cost more, but most people don't mix them, so I won't go into details. Minion Tap does not stay in play (which is a benefit to decks that recycle cards) and does not cost additional for playing more Taps on the same vampire. Decks that intend to refill large vampires (Renewed Vigor, Voter Captivation, etc.) will prefer Minion Tap to keep going back to the same source.

There are some other pro/cons to get into, but that's the basics. You'll usually favor Villein in decks that want to recoup from each vampire once, but Minion Tap for repeated pool recovery and/or larger vampires. Master package space and recursion have an impact on choice as well, but those tend to be lower concerns.

amazing. thought minion tap stayed in play too, but the wording is clear. my mistake. probably mixed the two in my head. What are common ways to cycle stuff like minion tap from the ash heap? because it burns after use, right?

You want to look to ashur tablets mainly because yes, it go to the ash heap after you have used it.

How many ashur tablets would typically go in a deck? is there a general rule of thumb that dictates how many copies you want in to et a key card out? I guess with permanents you dont want too many as they cut up the deck too, right?

also, is zillah valley a popular/strong card? its in both keepers 1 and the lasombra precon and I just feel it would be super sketchy to actually play. it pings you for 5 (thats a LOT) and nets a vamp 4 blood. seems brutal.

The number of card in a deck is a really tough question because the answer would be "it depends".

For example, my personal rule of thumb for a card I really NEED in the beginning of the game (like Zillah's ^^) is about 8 out of 80 cards.

For ashur, it would mainly depends about the reliability of your MMPA enabler (Multiple Master Phase Action). If you count only on Parthenon, it is really tough in my opinion to play more than 6 or maybe 9 but if you play vampire like Nana Buruku or Cybele (or both), some people goes to crazy numbers like 21.
Classicaly, you want your ashur number to be 4 out of 60/65 cards (to reliably have 1 cycle) or multiples of 3.
Actually, when you reach numbers like 15+ the fact to have strictly a multiple of 3 is a psychological matters because you will discard some and the chance you will play all 21 of your ashurs for example is about 0%.

Now about Zillah's Valley. I think you missed something.
The cost of the card is not really 5 pools but is actually 1 pool.
You pay 5 but 4 beads go from the blood bank to a vampire in your uncontrolled meaning you have to invest 4 less pools to bring it out.
So effectively, you will pay a master phase action and 1 pool to gain 4 transfers right now.
If you have 4 transfers, you can bring out a 8 cap in 1 turn instead of 2 (which is huge !)