Chests

Chests are unlockable and will contain Gear and or Items and or Gold, which is dependent on your current level. There are Gold Chests and regular chests, each can be bought with Gems or can be bought with real currency.

Description
Chest contains Items and Gear of different rarities depending on chest type. It is possible to find shiny gear which increases the effect of this gear by 50%. Each Event has its own kind of chest which works on the same way as the regular silver and gold chest with one exception. The dropped Gear belongs to the Event related Champion.
 * Silver Chests contain 3 cards (Common to Uncommon rarity). They always contain one equipment and one gold card. There is a chance of dropping “Rare” equipment cards, but they do not contain “Epic” equipment cards.
 * Chance of a Rare drop in a Silver Chest is approximately 3.2%. (Source)
 * Gold Chests contain 5 cards (Uncommon to Rare rarity). They always contain two equipment cards (at least one Rare), one bounty contract and have a chance of dropping an Epic equipment card.
 * Chance of a Rare drop in a Gold Chest is 100% and an Epic drop is at least 10%. (Source)
 * You only get gear in chests up to the highest Champion you've unlocked. (Source)
 * Gold chests should be opened immediately, as they contain 5 Items, which can be either usable or Gear for your Champions.
 * Silver chests are better to be opened at the point when you're about to reset.
 * Silver chests contain lower tier Gear and gold, which is why you want to use it later, since amount of gold you receive seem to be dependent on the the level you are on right now.
 * Which chests to buy?
 * Usually a personal preference, honestly. But having a chance to get one or two very, very powerful items in a Gold Chest seem much better than getting ten mediocre ones. However the math could be different to see which is better in the long run.

Champion Chests
All event champion chests are also available via their respective Time Gates in a limited amount.

Patron Chests
Each Gold Patron Chest contains five cards between uncommon and epic with gear for Champions who meet Patron's qualifications.

Misc Chests
''Note: Electrum Odds
 * Gem Cards:
 * - Common - 10 gems [25%]
 * - Uncommon - 25 gems [60%]
 * - Rare - 100 gems [15%]
 * Items (Only Owned Champions):
 * - Common - [35%]
 * - Uncommon - [55%]
 * - Rare - [10%]
 * Potion:
 * - Guarantee at least uncommon
 * Blacksmith Contract:
 * - Guarantee at least uncommon
 * Bounty Contract:
 * - Common to Rare same odds.