The Blue Scribes

Instead of moving in their Movement phase, any CHAOS CHARACTER can, at the end of their Movement phase, attempt to summon a DAEMON unit with this ability by performing a Daemonic Ritual (the character cannot do so if they arrived as reinforcements this turn, or if they themselves have been summoned to the battlefield this turn). 

If they do so, first choose one of the four Chaos Gods - KHORNE, TZEENTCH, NURGLE, or SLAANESH. A CHARACTER who owes allegiance to one of the Dark Gods can attempt to summon the units of their patron - for example, a KHORNE CHARACTER could only attempt to summon KHORNE DAEMONS. 

Roll up to 3 dice - this is your summoning roll. You can summon one new unit with the Daemonic Ritual ability to the battlefield that has a Power Rating equal to or less than the total result so long as it has the same Chaos God keyword you chose at the start (in the case of units that have the choice of allegiance, such as Furies, the unit when summoned will have this keyword.) This unit is treated as reinforcements for your army and can be placed anywhere on the battlefield that is entirely within 12" of the character and more than 9" from any enemy model. If the total rolled is insufficient to summon any unit, the ritual fails and no new unit is summoned.

If your summoning roll included any doubles, your character then suffers a mortal wound. If it contained any triples, it instead suffers D3 mortal wounds.