So... I have a question about the level 40 water spell Create Liquid.

In it it says that the spell can be altered to produce less liquid if the presence is higher than that of water.

Here is my question though. What is the presence of water for one? and for two what would be the presence of a liquid such as acid?

The idea I had was dropping 50k Liters of Acid (or at least the presence equivilant) on top of a battlefield at one point in my career as a Wizard Mentalist.

Create Liquid create 10 liter of water and then double it for every extra effect.

However for balance sake it should not be applied as a power but rather a "+100%" otherwise a wizard with 20 in INT pourring the very maximum zeon (400) into it could summon : 10*(2^32) = 42949672960 liters. that is a ludicrous amount. This is 42949672,96 m³. Remember that this is a lvl40 spell you're not supposed to be able to recreate the Noah's legend with it no matter how powerfull you are.

So now that this is out of the way the very maximum you could do would be 10 liter of water multiplied by 33[100%(base value) + 3200% (32 extra effect) : 330 liter of water.

So even in water you're not even close to do the same amount in water as what you wanted to do acid wise.

About the water presence it is nowhere to be seen however it should be easy to guess that any other liquid being more interesting/sophisticated/usefull etc...that water has neceserraly a low presence value and that it is up to the game master to rule the ratio. For exemple : an Acid is a very usefull and potent liquid so i would probably rule that it has at least five times if not ten times the presence of water effectively dividing the initial amount by 5 or 10 respectively.

Well, how much you can create does depend on both GM interpretation and whether or not you're using Core Exxet Rules. I really don't see a reason why a person with 20 INT (which is insane, by the by) shouldn't be able to cause catastrophic flooding like that, but the numbers may need some taming.

Core Exxet says a Wizard with 16 INT can summon 50,000 liters, and anything higher doesn't really change that.

So, let's scale down to an INT 16 Wizard (much more reasonable in the first place), which would give us 320 Max Zeon. The English Core says it's 2 gallons at 80 Zeon, doubled for every 10 after that. Two gallons roughly translates to 7.5 liters, but since Anima likes multiples of 5 let's put it at 10 liters (that may be what the original Spanish says anyways).

320-80= 240/10 = 24.

So it's either 10*(2^24) = 167,772,160 liters (which is already much more reasonable)

Or 10*25= 250 liters, which is pretty pathetic compared to Core Exxet.

Now, there are some huge gaps between 250, 50k, and 168 million, so where your GM wants you to end up is up to them. But considering that other Level 40 spells can do things like a 220 PsR/MR check in a 4000 ft radius around the caster at INT 16, or give +280 points to split between secondaries, I'd be tempted to adjust the math to make it closer to the second option myself.

Presence is also definitely GM territory. I do agree though, depending on the acid I'd definitely do a ratio multiplier as Aryador suggests.