[Shovah32]

I haven't seen any of the summons above level 5, and not all the ones below it.
Zmeys are great chaff killers. With multiple attacks, decent health and firebreath they are very handy.

The Lady Midday is probably my favourite. Ethereal, fear and flying allow them to reach the enemy quickly and scare off many weaker troops. Any who stay around for a while often get cut down by their Scythes(19 damage magic weapon at 11 attack and causes disease?).
On attack rear or archers, they are monsters. Most troops back there, other than very high defence rear-guards, will fall to these guys. Archers will run(8 routed 30 archers in 1-2 turns) and commanders - particularly the giants I was fighting, get cut to pieces.

If you can get the mages, 1-2 castings of Send Bukavac will take out most underwater independants. Follow it up with either a flying, amphibious commander(I like to give my fivefold angels winged shoes, so a ring of water breathing can be added too) or a Send Vodyanoy spell(who can also search for many underwater sites) to get a nice hold in the water far away from your main empire. Get up a lab and you could start gating in troops to strike an enemy far away from under the sea.