Although the monsters Leon could summon using Mind Summoning didn't obey him, those creatures could give him coins, and he also could use Seal on them, unlike the monsters that that place spawned.
"Well, I can only summon monsters using Mind Summoning that appears in worlds that are on the second stage of assimilation," Leon said. "So, what kind of equipment should I do with it?"
Considering Leon's control, he could upgrade a piece of equipment many times. The question was, what kind of equipment could help him at that moment? One that could increase the speed of his training would be a good idea. Leon already had a ring that granted him a skill at the max level, so he knew very well how useful such an item would be. But by using a ring or any other type of equipment that may grant him Haste at its max level, he would lose the chance to level up the skill. It was better to be patient and master that skill and instead think of another.