Relic is an attachment card type. Playing a relic attaches it to a player, and equipped relics may be viewed by hovering over the player's avatar. If more than one relic is attached to a player, a UI element will appear specifying their relic count.
A relic is an attachment that is played directly on the player. Some relics have activated abilities that can be used by clicking on the relic icon below the player portrait.
Relic weapons are weapons that can be played directly on the player. These count as both a relic and a weapon. A player can only have one relic weapon at a time - playing a new one will remove the existing one. Relic weapons have Attack and Armor stats. Once per turn, a player with a relic weapon can attack either a specific enemy Unit, or if there are none, the enemy player. Attacking an enemy unit will deal deal damage to the unit equal to the relic weapon's attack, and deal damage to the player equal to the unit's attack. Attacking the enemy player only deals damage to the enemy player. Relic weapons never deal damage when defending.
Any damage taken while a relic weapon is equipped will be subtracted from the relic weapon's armor. If the armor goes to zero, the relic weapon is destroyed, and any additional damage will go to the player's health. Cards that give the player armor, such as Grit, add to the armor of a relic weapon. If you already have armor when you play a relic weapon, it is added to the armor total. If a relic weapon is destroyed, such as by Ruin, all armor will be removed.
Attacks with a relic weapon can be responded to with an Ambush unit - this will re-target the attack to the new unit. The attacking player can also be targeted by cards such as Lightning Strike that target an "attacking enemy".
A cursed relic is a type of relic played on the enemy player. This counts as both a curse and a relic. These will generally have some negative effect on the enemy.
Playing multiple relics
Playing a relic weapon while another is equipped replaces a previous relic weapon.
Playing a non-weapon relic has no effect on previously played relics or relic weapons. You may equip multiple relics at the same time. Multiple copies of the same relic may also be equipped.