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The Fire Warriors (or 'Wraith Drones') are made from Necron warriors & greenstuff.
Iridium armoured Commander:
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I used a Wraithlord and simply added a Jet-pack and some "missile pods".
Crisis Suits:
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I used Wraithgaurd, again with Jet-packs & "missile pods". The center model has the Command & Control nod and Multi-Spectrum Sensor Suite.
Broadsides:
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Used the same starting point as the Crisis suits, I added some extra armour plates and Typhoon missile launchers. I thought about using a different weapon for the Smart missiles, but since the actual Tau models use the same design for Smart missiles & Missile pods, I thought they looked fine.