The VOIDRUNNER'S CODEX is LIVE! Explore new worlds, fight oppressive empires, fend off fearsome aliens, and wield deadly psionics with this comprehensive boxed set expansion for 5E and A5E!
keep in mind that our slaad lords and altroloths are 3.0 conversions, and IIRC they were done before the ELH came out so they are not likely to be all that balanced...
however, you may have much better luck using the re-re-revisions that came out of them, most recently seen in ToH1 revised.