# Math:
# Lands = # of land permanents
# Exarchs = # of attacking Deceiver Exarchs
# Rest = # of other non-lands permanents (ignored because doesn't change asymptotic probabilities)
# Life = player's life
# probability of hitting a land P_stop = Lands/(Lands + Exarchs + Rest)
probability of sacrificing N Exarcs = (1-Lands/(Lands+Exarchs+Rest))*(1-Lands/(Lands+Exarchs+Rest-1))*...*(1-Lands/(Lands + Exarchs + Rest-N))Lands/(Lands + Exarchs + Rest)
# Expected number of permanents to be sacrificed:
sum for i 1-Lands/(Lands + Exarchs + Rest - i)
asymptotically, only x=number of exarchs matter
probability of sacrificing N Exarcs = 1/(x) * product 1-1/(x- i), i = 0..n-1 = (1 - n/x)/x
expected surviving: x - sum n * (1 - n/x)/x, n=0..x = x-(x^2-1)/(6 x)