At its most basic level, a mala used 108 beads to count down the recitations of a mantra. One mantra is one bead, and you turn the mala in your hand as you chant in order to keep count. Chanting a prayer 108 times is meant to represent chanting for a full day, and as you can imagine, there's a certain spiritual weight to doing so.
Each and every utterance of the words acts as a kind of spell that creates a connection with Divinity. This can be a connection to a specific aspect of Divinity through a specific God, Goddess, etc., or it can be used in a general way by using mantras like Om Mani Padme Hum. This connection is then created within you and rooted into the tool used to count out every recitation. In a quite astounding way, actively praying through mantra creates a ripple of energy which then emanates out from you and changes those around you by extension.
As such, each and every utterance is a sacred thing, so naturally the mala gains strength as time goes on & the more mantra you accumulate, the more strength is gained. This isn't a hugely transformative thing at 108 recitations, but 108 recitations a day for 30 days is 3240 mantras. All for five minutes a day.
As you do this for months and years. that all adds up. The mala builds in power and potency, becoming a sacred tool unto itself, and that sacrality can be tapped and applied. In short, this case the mala can become both a focus for prayer and a means of sorcerous action.
If you intentionally direct the energy within this tool towards a specific task related to the mantra itself, you add to the spellwork you perform while doing so. You are, in essence, channeling your dedication into a physically manifest object and then later using that stored energy to create great change.
To use the prior example, if you chant "Om Mani Padme Hum" each and every day with this in mind, that mala will become a receptacle for this energy. Thus, it can be used to create a kind of mindful compassion in others that can be used to better friendships, create gains, and otherwise change your life for the better while acting as a positive influence on others. You become a nexus for that energy and then it manifests through you.
The same can be said for heavier mantras and practices by extension, though I would suggest a bit of caution if you're looking to work with beings like Vajrakilaya, Yamantaka, or Chakrasamvara.
This same technology can be used in conjunction with demonic enns or prayers you write. This is both a means of generating a powerful connection with the spirit & a tool for manifesting change you seek from that spirit. I've done such a thing for others in the past as a means of increasing the fluidity of evocations and spellwork done in their name, and it works really well.
Its potent stuff, so do give it a go if this inspires you.