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M6 WS2 BS0 S2 T2 W4 I4 A4 LD5 w/ Forest spirit, Ethereal, Swarm
M6 WS3 BS0 S3 T3 W5 I6 A5 LD5 w/ Forest spirit, Scout, Swarm
M6 WS2 BS0 S2 T2 W4 I5 A4 LD5 w/ Forest spirit, Regeneration, Swarm
M6 WS3 BS0 S2 T2 W4 I6 A5 LD5 w/ Forest spirit, Poison, Swarm
Here's three different verisons!
A swarm needs poison to get any kills of. So because of that I choose poison.
But for a special choice I think this is a bit marginal... only 1 "Special" thingy? I dont think I would ever field them... Maybe give them some special rule that enables the to be fielded anywhere inside a forest or in the deployment zone... sort of a semi-scout.
Well if you look at other swarms, they have similar stats, swarms are unbreakable remember, they can allow others to line up charges.
I like the Ethereal swarms. with ethereal I would charge with thier impressive movement 6 to tie up a unit of RnF infantry as long as the unit does not have access to any magical attacks. this would give my wardancers a chance to flank charge the unit and bing bam boom the swarm unit just made back it's points. I think any ethereal unit in the Wood Elf list would make for an incredible asset.
An unbreakable etheral thing would be too over powered. Can't justify a S3 on a swarm. Regen would be a nice touch and would make sense. Poision is also a nice touch.
Balence wise, If you want a more defenceive one, #3 is balenced for it. #4 is a goold balenced one if you want a more killing one.
I dropped swarm, and made them similar to the Spirit host.