Enchantment Necrosynthesis Enchant creature Enchanted creature has "Whenever another creature dies, put a +1/+1 counter on this creature." When enchanted creature dies, look at the top X cards of your library, where X is its power
Heres an example of what a mobile board state looks like: Lands go left, artifacts and enchantments go right
The other reason to not overload on learn cards is there are diminishing returns casting Lessons
For example, the Giants Unleashed mission wants you to get Regigigas, Regirock, Regice and Registeel while the Battle with Champion Cynthia mission requires Cynthia, Garchomp and two Spiritomb
Some are too slow, while others are severely countered by popular meta decks
To increase the chances of drawing key cards during play its most common to have exactly 60 cards and run 4 copies of important cards