it says 50% bonus xp, so I'd think that petrify a level 5 and kill a level 5 is a net win, since you don't have to fight the other level 5 and still get full xp. Is this right?
Can you petrify a level 1 and get double xp for a level 5?
so I'd think that petrify a level 5 and kill a level 5 is a net win, since you don't have to fight the other level 5 and still get full xp. Is this right?
You absolutely do not get full XP here: ignoring bonuses due to level difference, a level 5 monster gives you 5 XP. If you kill both, you will get 5 + 5 = 10 XP. If you petrify the first one then kill the second, you will get 0 + 5 * 1.5 = 7.5 XP, rounded down to 7. In your example, you would therefore "lose" 3 XP by using IMAWAL (compared to the 10 XP you get by simply killing them both).
If you do not want to lose any XP from the IMAWAL glyph, you need to kill a monster which level is at least twice the level of the monster you petrified. For instance:
Not really impressive as a bonus XP generator so far. The interesting part of the experience boost is that the XP bonus due to level difference is multiplied by the 50% IMAWAL bonus (source).
Back to my first example, if your character is level 2:
Now, I think the most interesting way of using the IMAWAL glyph is as part of "the Earthmother engine":
Since the cost of Entanglement does not increase when you use it, this engine is "piety stable": you can repeat the process as many times as you need, making it an efficient way to grind XP all the way up to the boss.
You want to petrify the lowest level mob you can so you don't waste xp. The game is all about maximizing your experience gain through petrify, slows, and kills of higher level mobs.
You can petrify a level 1 and get exp on any other mob. The only requirement is that it can't be a boss you petrify.
Source: http://www.qcfdesign.com/wiki/DesktopDungeons/index.php?title=IMAWAL
From the wiki:
Petrifying enemies does not count as a kill and rewards you 0 XP
So you have to weigh the bonus 50% XP from the next monster you plan to kill against the lost XP from the monster you petrify.
My current rule of thumb is to try to petrify a level 1 and then kill a level 6 or higher.