Warlock Invocation: Tome and Blade

[Garresh]

I have a player who basically wanted to play a warlock whose fighting style is based off of Robin from Fire Emblem/Smash Bros. As is, there's no benefit to actually wielding your tome during combat, especially if you're in melee and could use a shield instead(they're going hexblade). I wanted to make an invocation that I thought might encourage a Tome pact warlock to fight in melee a bit. Anyways, here it is. Please give your thoughts!

Tome and Blade
Prerequisite: Pact of the Tome Feature

Whenever you cast a spell using a warlock spell slot granted by pact magic(not invocations or mystic Arcanum) you charge your blade with eldritch energy. Until the end of your next turn, the next melee attack you make gets a bonus to damage equal to the level of the spell used to charge it. Whenever you make a melee attack on your turn, until the end of your next turn you gain a +1 bonus to your next spell's attack, damage, and save DC. You may only gain this bonus once a turn, and only on your turn. If you stop holding your tome for any reason all active bonuses are immediately lost.

[Kane0]

Not bad. I'd perhaps limit it to level 5, but seems solid. You could probably even take out the Pact-Magic-only part, since it's only until next turn.