Emerald characters also tend to have keywords like ward and evasive, which make interaction through actions or challenges a nightmare for opponents
If the pack has a Rare or Mythic you don't already have 4 of, you should take it, period
Can you discard at will if someone has a bounce spell
After all, this Lhurgoyf has long since been a Constructed staple since its first printing in Future Sight , since it can rapidly grow bigger and bigger without an additional investment of mana (and it only costs two mana to play)
This evaluation is given based on being able to get any lesson whenever these cards trigger with no need to pick or include the lessons at all
Also note that you must use mana like normal, rather than Black's typical "you can spend any color of mana" so run things like Manaliths or Fellwar Stone instead of Commander's Sphere and Medallions as your leader