A Collection is a set of 5 items dropped from a specific enemy unit type (though new units sometimes also drop these items) which can be traded in for certain rewards, with 1 of each traded in for the given reward.
There are eight Collections in the game, which are in order:
- Scout Collection
- Infantry Collection
- APC Collection
- Artillery Collection
- Battle Tank Collection
- Stormtrooper Collection
- Rocket Battery Collection
- Versus mode collection
- The Scout and Versus items cost 1 Army Gold each.
- The Infantry and APC items cost 2 Army Gold each.
- The Artillery and Stormtrooper items cost 3 Army Gold each.
- The Battle Tank and Rocket Battery items cost 4 Army Gold each.