The Bats are somewhat like faster, aerial Skeletons, except they cannot be used to pull units that only target ground units.
They can be a replacement for Minions. However, they have significantly lower hitpoints, slightly lower damage and thus can be killed in one shot by many ground units that target air like Witch or the Princess Tower. They also pose much less of a threat when used for attacking.
Bats can be used to counter ground troops like Knight, Valkyrie, Mini P.E.K.K.A. and Bowler. They can quickly defeat the troops with their high DPS if not countered by spells or splash units.
The Zap is a neutral elixir trade for the Bats, though they may be used to bait the opponent into using their Zap for other swarms after that, essentially making for a new card to be put in spell bait decks.
They can be used to counter the Graveyard for a 3 Elixir profit. Be careful, however. The opponent may use a spell on the Bats to protect the Graveyard.
The Bats cannot counter the Golem very well because its Death Damage will kill them.
On 12/6/17, a Balance Update decreased the Bat count to 4 (from 5). The Bats had not been released at the time of the Balance Update.
The Bats card was made available as a one-time reward from a special Draft Challenge that started on 23/6/17, meaning the card could be unlocked before it was generally released.
From 30/6/17 through 3/7/17, the Shop had a special offer that Arena 8+ players can buy up to six Giant Chests at the normal price that guarantee at least 40% of total cards (or 50% of all common cards) to be Bats.
Bats have the same stats as Skeletons of equal level except they fly, they target air, have a very fast move speed, have two more bats and cost 1 more elixir.
Bats and Balloon are the only 2 flying troops with a melee attack range. Although the Balloon is solid melee and the Bats actually have a melee range of 1.2 tiles.
When the card was first announced, there was a mistake in the description stating there were "Four" bats instead of five, and many got confused as the count statistic stated the correct "5". The mistake was quickly fixed and the description was changed to "Five". The card was then nerfed, changing the description and number of Bats back to "Four". Then back to "Five" as of the 11/8/17 Balance Update.
It is the only card that spawns five of the same troop.