While holding this rod, you gain a +1 bonus to spell attack rolls and to the saving throw DCs of your warlock spells.

In addition, you can roll a d4+1 once per short rest, and depending on what you roll, you can summon demons up to that CR. 

One per long rest, you can change that 4d+1 into a d6+1.

One every seven days, the rod grants you the ability to double the dice. You may roll 2d6+1 instead.

The summoned creatures last one hour and require concentration or the demons will become hostile towards you. 

Notes: Bonus: Warlock Spell Attacks, Bonus: Warlock Spell Save DC, Warlock, Summoning, Buff