I like vestiges! And your work is quality - very thorough, very useful for actual play. I just happen to disappear for months on end without notice on occasion. If you've got others, do you mind pointing me to them?
As for Echidna here... I thought summon monster used a chart to determine which monsters could be summoned by level? I suppose it would be more concise to ask, for example: if a Level 5 Binder uses Summon Echidna's Spawn, which monsters could he summon?