Are you sure it wasn't a great karmic wyrm you summoned? I'm pretty sure the ancient karmic wyrm is sort of unique.
AFAIK, familiar summoning can get you any monster up to the danger level you're sitting at (although if you go too high you always get greater elementals). I've seen balors, greater molochs, great karmic wyrms, and emperor liches before. Greater earth elementals are still actually probably my favourite summon (regeneration, massive damage and PV, ranged attacks), and much easier to get than a lot of these since at very high DL, you get them about 1/3 of the time. Balors aren't half bad either, though.
Hoping to win with every class, doomed. Archer, Barbarian, Bard, Beastfighter, Druid, Elementalist, Farmer, Fighter, Monk, and ULE Priest down.