Zarakynel

If your Army contains a unit with the Arch-daemonic Ritual rule, they may instead of being deployed normally be summoned like other Daemons to the battlefield, although with greater risk to the summoner as befits their power and perilous nature. The usual rules for Daemonic Rituals apply with the following alterations:

When attempting an Arch-daemonic Ritual, the summoning player must first declare which unit they are attempting to summon by name beforehand, and only characters with the same Mark of Chaos as the unit you wish to summon can be userd to summon the unit.

When attempting to summon a unit using an Arch-daemonic Ritual, roll up to nine dice - this is your summoning roll. You can summon one new unit with the Arch-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 as the summoning character. This unit is treated as reinforcements for your army and can be placed anywhere on the battlefield that is within 12" of the summoning character and is 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 yourArch-daemonic Ritual summoning roll included any doubles, your summoning character then suffers a mortal wound. If it contained any triples, then the summoning character is slain instead (note that the summoning can still be successful, even if the summoning character perishes in the attempt).