The Ghost is a common Minion unit, that can be part of the Arcane Box. Other units can move through the Ghost since it doesn't block movement.
The SoulKeeper can transform enemy units into Ghosts.
Quick Stat: Ghost Edit
|Tier 1||Tier 2||Tier 3||Tier 4|
Tier 2: Ghost+ Edit
To Upgrade from Ghost to Ghost+, you need 5 Ghost and 25 Dragon Coins.
Changes from Ghost: Adds one move only in every diagonal direction
Tier 3: Ghost++ Edit
To Upgrade from Ghost+ to Ghost++, you need 5 Ghost+ and 100 Dragon Coins.
Changes from Ghost+: The move only is now move or attack
Tier 4: Ghost+++ Edit
To Upgrade from Ghost++ to Ghost+++, you need 5 Ghost++ and 500 Dragon Coins.
Changes from Ghost++: The move or attack now also has swap places with ally
Strategy: Ghost Edit
Strength: Ghost Edit
Line-based Champions (e.g. Rook, Bishop, Minotaur, ...) can be used much earlier in the match when a Ghost is placed in the otherwise blocking position in front of them. Ghosts can also swap with Portals to make them more useful, or even with diagonal-only units (such as Bishops and Mephits) to help them swap colors.
Ghosts themselves are very mobile, especially when upgraded.
Weakness: Ghost Edit
Enemy units can pass the Ghost, too. Ghosts can rarely be used for trading.
Like many Minions Ghosts have a very limited movement and attack range.
Ghosts are expensive.
Ghosts and Ghosts+ are completely vulnerable to diagonal attacks.