I am also interested in more information regarding the summon spells. I tried asking in Chris's blog commentary thread about the fact that the spells have wildly different XP requirements to GM. I kind of doubt that the summoned lich has more/better abilities "worth" the 7 or so million XP to GM it over a summoned fire elemental that costs about 4 million XP to GM. Summon water elemental is around 1 million XP to GM and these are huge sums in what seems like very tiny actual differences in their abilities.
I know the Water Elemental Pet in the Water Magic Tree will heal the player, while Bears did have knockdown, Spider Pets had Web and Poison and Corpions had Poison. Apart from the Elemental, I dont know if this has changed in the least few releases.
The Ice Elemental schould slow enemies, but sometimes this doesnt work, i use him rarely, what my changes now as the get better with Level
It seems to me like the new leveling curve (as of R41) of the summon spells does not improve their abilities. They seem to be doing the same damage as before, and as I have heard, the water elemental seem to be healing the same amount as before. So far I am not impressed with a summon spell at level 72.
When I began using a Phoenix a couple of releases ago, it averaged 8 to 12 damage versus the Kobold Fighters in the mines; this was at level 1 skill. Come r41 and my Phoenix is now level 36... but I see no difference in damage or ability. @Chris ?