How many enemies is a good amount per marine, currently running a campaign with 6-8 marines. Usually split into two groups during the game.

We'll that depends on how tough the enemies are and how well you run them. Properly handled ONE eldar can be a challenge to a marine if the gm runs the eldar like a cunning,intelligent being who may have eons of experience and advanced gear, but is afflicted with overwhelming arrogance and contempt for the ''Mon keigh'' he considered to be little more than vermin.

He'll, one eldar farseer can be a challenge for a whole death watch unit if ran properly.

In a one on one shooting match a single necron has a **** good chance against a marine. If you make it a case where it's not just a hopeless stand and shoot fest a marine has a chance to outwit and out think a necron automaton. I could see one marine defeating a squad of necrons if he lured them into the ruins of a city and collapsed a badly damaged building on them with a few well placed crack grenades, for example.

You don't need a swarm of mindless, screaming cannon fodder to 'challenge' a marine with numbers. Try running a few enemies who think and plan like intelligent beings.

We'll that depends on how tough the enemies are and how well you run them. Properly handled ONE eldar can be a challenge to a marine if the gm runs the eldar like a cunning,intelligent being who may have eons of experience and advanced gear, but is afflicted with overwhelming arrogance and contempt for the ''Mon keigh'' he considered to be little more than vermin.

He'll, one eldar farseer can be a challenge for a whole death watch unit if ran properly.

In a one on one shooting match a single necron has a **** good chance against a marine. If you make it a case where it's not just a hopeless stand and shoot fest a marine has a chance to outwit and out think a necron automaton. I could see one marine defeating a squad of necrons if he lured them into the ruins of a city and collapsed a badly damaged building on them with a few well placed crack grenades, for example.

You don't need a swarm of mindless, screaming cannon fodder to 'challenge' a marine with numbers. Try running a few enemies who think and plan like intelligent beings.

^ This.

There are three ways to challenge a group of marines.

1 - Hoards. Massive quantities of enemies throwing themselves at the party will slowly grind them down, little pings here and there will start to build. A marine can dodge but not against dozens of shots and will start to grind at their health slowly. It'll also start to chew up their ammo reserves like nobodies business. It's an effective tactic if you can get it working as with ever greater numbers there is the risk of panic and disruption.

2 - Massive enemies. A single MASSIVE target can prove a difficult foe to handle. Huge amount of health and some good damage can really challenge a party as they try to take it down. Bare in mind though that a massive enemy will mean players throw their all at a single target and all of their abilities so it'll need to be built to survive and ideally have a good few AoE or disruptive effects to keep them on their toes. Use with caution though as strong enough enemies will one shot players.

3 - Elite small group. A small group of well trained soldiers or the right guys in the right place can really do some damage. A group of XV-8 crisis suits, with their high mobility and jump packs can be utter nightmares to deal with. They can keep the marines out of melee range if allowed to fly onto structures and reign death from above, requiring careful tactics to outwit. Or a few heavy gunners to suppress the marines advance while snipers take careful aim to pick them off can be equally effective and force them to think on their feet.

One way to handle numbers is to simply introduce more on the fly. You don't have to have everything on the board straight away. If for example the players are attacking a squad of Tau Fire Warriors on the battlefield and you think that the marines are having too easy a time of it, introduce more opponents a round or so in while the fight is ongoing. Perhaps one of them managed to radio out for assistance and soon after, a second squad enters the field from wherever is most appropriate. Or perhaps some Kroot come charging in to tie them up and free the fire warriors. Never be afraid to change the numbers as the situation requires it. If you added too many you can always have some of them withdraw if the situation warrants it. Perhaps getting called away elsewhere or needed elsewhere and getting overconfident.

1.5/per player genestealers when you're starting out

2/pp at low rank

3/pp at mid rank

then for the brood lord fight add more or less depending the situation/terrain/fate points/etc.

There's a huge difference between killteams who use squad mode abilities effectively and those that don't - or not at all. The books themselves point out that GMs should bear that in mind when creating encounters.

If you're new to Deathwatch, I recommend starting with smaller numbers in the first mission or two, and then ramping up. Easy to justify, not every Deathwatch mission is about slaughtering enemies. Some are much more subtle.

There's a huge difference between killteams who use squad mode abilities effectively and those that don't - or not at all. The books themselves point out that GMs should bear that in mind when creating encounters.

If you're new to Deathwatch, I recommend starting with smaller numbers in the first mission or two, and then ramping up. Easy to justify, not every Deathwatch mission is about slaughtering enemies. Some are much more subtle.

Exactly.^

Seriously, the best way NOT to run a kill team member is the stereotypical image of an adeptus astartes. ''Argh! Me space marine! Me serve emperor! Me hate alien scum! Me shoot alien with gun! Me hit alien with chainsword! Me say 'For the emperor!' Argh!!''.

Honestly I encourage anyone who wants to play death watch right to read some 40k novels featuring space Marines. ''Dead sky black sun'' is a good one but there are more.

There's a huge difference between killteams who use squad mode abilities effectively and those that don't - or not at all. The books themselves point out that GMs should bear that in mind when creating encounters.

If you're new to Deathwatch, I recommend starting with smaller numbers in the first mission or two, and then ramping up. Easy to justify, not every Deathwatch mission is about slaughtering enemies. Some are much more subtle.

Exactly.^

Seriously, the best way NOT to run a kill team member is the stereotypical image of an adeptus astartes. ''Argh! Me space marine! Me serve emperor! Me hate alien scum! Me shoot alien with gun! Me hit alien with chainsword! Me say 'For the emperor!' Argh!!''.

Honestly I encourage anyone who wants to play death watch right to read some 40k novels featuring space Marines. ''Dead sky black sun'' is a good one but there are more.

Especially in the Deathwatch, which value flexible thinking in its recruits.