When you cast Summon Aberration, you can modify it so that it doesn't require Concentration. If you do so, the spell's duration becomes 1 minute for that casting, and when summoned, the Aberration has a number of Temporary Hit Points equal to your Warlock level plus your Charisma modifier.
In addition, the first time each turn the Aberration hits a creature under the effect of your Hex, the Aberration deals extra Psychic damage to the target equal to the bonus damage of that spell.
{
"name": "Create Thrall",
"page": 163,
"level": 14,
"__prop": "subclassFeature",
"header": 2,
"source": "XPHB",
"entries": [
"When you cast {@spell Summon Aberration|XPHB}, you can modify it so that it doesn't require {@status Concentration|XPHB}. If you do so, the spell's duration becomes 1 minute for that casting, and when summoned, the Aberration has a number of {@variantrule Temporary Hit Points|XPHB} equal to your Warlock level plus your Charisma modifier.",
"In addition, the first time each turn the Aberration hits a creature under the effect of your {@spell Hex|XPHB}, the Aberration deals extra Psychic damage to the target equal to the bonus damage of that spell."
],
"className": "Warlock",
"classSource": "XPHB",
"subclassSource": "XPHB",
"subclassShortName": "Great Old One"
}