Crystal ooze on a successful hit, causes 1d6+1, plus 1d6 acid, plus grab, plus toxin for Fort save DC20 or become paralyzed for 3d6 rounds? That seems pretty harsh for CR4. Plus its immune to lots of stuff. What am I missing? I'm afraid it's going to kill my four 5th level players.
You're missing that it has a speed of 10'. This isn't something that players should instinctively run up and whack.
It's also effectively an omnivorous booger. Easy to distract with food thrown one way ... or a hamstrung (character smaller than me) ...
