[Gregstrom]

There aren't really any helpful summons. If you have Death then spectral mages have some chance of S1 or perhaps even S2 turning up. Tartarians can get at least S2, I believe. Blood nations can summon (with luck) an Ice Devil or Arch Devil with some levels in Astral.

Basically, Astral doesn't ramp up with summons in the way Death does. The nearest you get are Ether Lords (S3, 1 in 4 are S4), an S4D1 summon for 90 pearls, and Golem who are S2 and need S3E2 to summon. Neither is much help in ramping upwards.

Site searching is a better bet, as there are sites providing Astral mages that can be found without an Astral site search. 1 in 4 metal order adepts have S3, which is as good a start as you'll probably find.

Failing that, there are Crystal Amazons (10% get S2) or lizards (all N1S1).

You can in theory use item boosts to go from S3-S9: Dimensional Rod + Skullcap + Robe of the Magi + Ring/Crystal Coin + Forbidden Light = 6 levels in S. However, you'd have to be starting with an F2S3 mage and already have Blood/Air mages and a sizeable lead in Con research to get this. And of course the recipient of these items would suffer from rapidly mounting insanity and quite a bit of horror marking.

If you did this, you would be well advised to make your first wish for a Seraph (or maybe a Stargazer - a R'lyeh hero with S5) and then empower them up to S6 so they can spam wishes without having to equip unpleasant artefacts.

To be honest, as long as you've been clamming heavily enough to get an Astral income of 100/turn it's more a matter of time than anything else. If you've saved up 250 pearls over the game, have an income of 10/turn and a couple of lizard shamans, then you aren't going to get very far. Thus, the most reliable (and possibly easiest) way is to try and clam constantly from the moment you research Con 2.