Ok I am in my first campaign n the 2nd easiest difficulty level. I think I am on shard #12 and am right next to Beleth's castle with a L16 Warlord(yes I realize that was a mistake now) with the following Horse archers level 8,8, 7,1&1. Priests 5&1. Swordsmen 11,11 &10. Healers 10&8 Crossbowman 6. I have Off tac 1, leadership 3, maneuvering 3, Ranged tacs 3, logistics 3, combat 1, def tactics 1 and discipline 2. Is there anyway I can get past the phoenix? Will he run out of money to pay it if I take all his other provinces? Or am I screwed?

I have a level 5 scout but no building for hatching Spider eggs or one for advanced necro spells.(haven't had either one offered) So scout to sniper it is! Any idea how high level I should have him to kill the thing? And thanks!

Based on available bow/crossbow.
In your situation would be easier to attack at the same turn in 2 waves:

1. First goes scout. He must heavily wound phoenix and die without activating its reincarnation - probably you can do it with some cannon fodder right away. Give him good crossbow, 6-7 units, he would be able to shoot 7-8 rounds for 8-10 damage. If you hired scout after commander, he will go first.

2. Commander with crossbowmen attacks wounded phoenix. 15 crossbowmen under ranged tactic 3 would be able to kill it. Fresh crossbowman have 5 damage +2 from ranged tactic, probably +1 from morale. So, 8 raw damage. They ignore half of the ranged defence, so even if your phoenix have 8 ranged defence, they would be able to deal 15*4=60 damage in first round, 14*4 = 56 in second, 13*4= 52 in third. Enough for fresh phoenix. (Commander/scout multiclass so much better for this with its +4 damage to ranged units...)

Vampirism is pretty common in drop, by my experience.

Nice tips, Gremlion!

Any advise you can give on defeating a 'phoenix cult'? Apparently I have a few in my starting ring but they come with a lot of friends like gryphons etc. I currently have a sniper and will probably be getting to level 3 buildings soon [playing single player].

Is there some suitable army composition and army tactics? I have got a cult of hydra next which looks even more juicy but has tougher opponents [at least in my perspective]!

One minor addition to the excellent tips from Gremlion - get quiver with 'heavy ammo' bonus. It gives -1 to ranged defence for three turns (cumulative basis). So assuming you can get double shot on your scout it's possible to get -6 to ranged defence by third turn. Obviously, you can ignore if you have better quivers.

One easy way to obtain is second tier archery shop, sells 'heavy arrows'. BTW, it's a one of the better quivers as it has durability of 30 which is one of the highest for quivers. Takes longer between repairs and amplifies damage of other ranged units (if present). Obviously, doesn't work as well versus targets with low or none ranged defence.

Thanks I'll look for the quiver. I have some of the arrows but never noticed the quiver.

Well I had to build 3 forts near Beleth to stash all but one of my tier 2 units(didn't want to lose them) however using 14 l1 crossbowmen and one L11 Horse archer I couldn't find room for in a fort I killed it in 3 turns with the lose of 3 crossbows!

Well done!

Fun fact about the Phoenix guard: When killing it, you can sometimes loot a phoenix egg. So once I posted a phoenix guard, and the enemy killed it with heavy casualties, but looted a phoenix egg! Next thing I know he comes back with a phoenix in his army.

I really need to find that monster hatching building then.