Evening all. Currently playing a Promethean Mage and found a potential bug. Summoned a Wyrmling on Level 2 3 of the dungeon, then went back up to level 2 to sell some things in the shop then came back down the same set of stairs to level 3 and re-summoned wyrmling. I now have 2 wyrmlings as allies.
Floor changes and save-and-exits don't seem to save the 'this creature is summoned' flag, just the 'this creature is friendly' one. If you summon a wyrmling, save and exit, reload, summon a wyrmling, and repeat ad nauseum, you can get an arbitrarily high number of wyrmlings.