One of the big issues you may encounter as a Game Master is how completely overwhelming Magic can be. It can achieve just about anything, after all, and there is no hard limit on how many times your Wizards will obliterate things with their selected attack spell. If things seem to be going too well for your Wizards, they’re either very good at what they do, or you haven’t considered all the ways in which an otherwise successful spell can go wrong.
Just because a spell works, doesn’t mean there aren’t unintended consequences.
Assuming they manage to create a powerful fireball type spell, then it is bound to be extremely destructive. Everything it hits will catch fire, be broken, smell absolutely disgusting or explode. If the Wizard is in a confined space they will want to stand well back, but even then the air will be ruined, and if they needed something in the blast zone then that’s all history now.
Vaporising the giant centipedes that are crawling towards them is also unlikely to yield the desired benefits. The spell is going to need to target the area just to cover multiple targets, and will need to be limited to the animal material elemental quality or bits of dirt, stone, and vegetation are going to get included in the area of the effect. Worse than that, you end up with a large amount of super-heated material expanding into the available air supply.
There is no magical healing in Grimoire in the manner you might be used to. A Wizard can produce a similar restorative effect by simply transforming the injured person into an uninjured version of themselves. This works even if the injured person has lost a limb, although they may end up being somewhat shorter to account for the lack of physical materials. It also relies on the Wizard being quite certain how everything was supposed to look in the first place. The transformation is stable, and will eventually become permanent, but any kind of magic cancelling spells or sources of Inarcanide should be avoided.
Transmuting a target into stone will transmute them body and soul into rock. It is very important to note that the human body is, for the most part, not solid, and the outcome will be a statue containing red-hot lava where its body fluids used to be. The first thing to realise is that, under these conditions, this is not going to be a whole statue for very long. The second thing to realise is that, if the magic is undone, they are going to need a mop.
Transforming a target into a stone statue will prevent the explosive consequences of a transmutation. It will create a statue of solid stone, body and soul, and reverting the statue from this state does not restart neural and bodily processes. Achieving those will require some clever preparation or quick thinking.
In conclusion, it is far easier to cast a broad-effects spell than to focus the spell phrase down appropriately. It is extremely easy to cast a spell without thinking through all the negative consequences of that spell, especially when working under pressure. It’s not necessary to rely on Spell Bursts for the situation to start spinning out of control