Can you please stop the ridiculous beelining of Contingency fleets towards the player?

[Eladrin]

Pretty sure this is actually intended behavior. The Contingency's designed to specifically target the single greatest threat to it in the galaxy and assault that, based on weights like Fleet Strength, Megastructures, etc. The Unbidden do something similar, except they select an at-random Nemesis to focus on, influenced by stuff like how many wormholes you've got in your territory and if you host the Chosen One.

This is correct. The Contingency considers you the biggest threat. It also does its best to link up the hubs and take as many megastructures as it can.

The Unbidden are fond of holes in space (like wormholes or gateways), psionic targets, and especially the most delicious soul of all, the Chosen One.

The Prethoryn look primarily for things they can eat.

 

[Eladrin]

That is interesting! Does this mean the Pethoryns tend to ignore machine and synthetically ascended empires?

To a degree, yes. Given the choice between two targets, with all other variables being the same they'll weigh the one with living pops higher than the one with machine pops. They might still go for the other, but they'll weigh the living pops higher. (The exact multipliers are in defines.)