Upgrades and Fusions

Nearly all cards can be upgraded using salvage points:

Level 2: 5 SP
Level 3: 15 SP
Level 4: 30 SP
Level 5: 75 SP
Level 6: 150 SP

Commons are only upgradable to level 3 and rares are only upgradable to level 4. Commander upgrade costs are double assault or structure upgrade costs

Most fully upgraded base set epics and legends (as well as a few rares and commons) can be fused with certain other fully upgraded cards in order to make new cards. That is, fusing cards takes existing cards you have (fusion components), removes them from your inventory and gives you new cards instead.

You cannot unfuse a card to retrieve parts which you used in a fusion.

One can fuse cards to make dual or quad fusions.

duals and quads

Dual fusions take two (or up to three, in the case of some base set) very specific, fully upgraded cards and fuse them into a more powerful card. Rarity of the fusion will be taken from the highest rarity of the cards used in the fusion components.

You can take up to three specific cards, at least one of which is a dual, and fuse them to make quad fusions, which are stronger than duals.

Since late 2014, during each event roadmap, developers release a "cycle" of free-to-play or base set fusions, one card of (generally) the same rarity and type (assault or structure). All released base set quad fusions can be found here:

visual history of fusions

Apart from base set fusions, there are also rewards cards from missions and events. Rewards cards follow a very specific fusion formula: two copies of a fully upgraded single make a dual, and two copies of fully upgraded duals make a quad. No rewards cards has a formula using three cards to make a dual, or three cards using at least one dual to make a quad, unlike some base set cards.

separate rewards list

There is however one reward fusion that uses two different faction cards to make a quad - Barracus Redeemed.

Not all base set fusions or rewards cards are useful, and there are many outdated and totally useless cards in the game.

A sample list of the best cards to make and cards to avoid making can be found here:

tier list

Apart from base set cards and rewards cards, developers also sell cards to players thru the store