The Tenser's transformation spell description (Xanathar's Guide to Everything, pg. 168) states:
You endow yourself with endurance and martial prowess fueled by magic. Until the spell ends, you can’t cast spells, and you gain the following benefits:
[…]
- You can attack twice, instead of once, when you take the Attack action on your turn. You ignore this benefit if you already have a feature, like Extra Attack, that gives you extra attacks.
The description of haste says:
Choose a willing creature that you can see within range. Until the spell ends, […] it gains an additional action on each of its turns. That action can be used only to take the Attack (one weapon attack only), Dash, Disengage, Hide, or Use an Object action.
If wizard A casts the spell Tenser's transformation on himself and wizard B casts haste on A, does this allow A to perform 4 attacks?
In other words: does the fact that haste gives an extra single Attack action prevent Tenser's transformation from triggering?
Best Answer
Wizard A gets 3 weapon attacks
Tenser's Transformation says:
So, when the wizard uses their normal action to Attack, they get to take 2 attacks (per Tenser's Transformation).
When they use the special action from Haste to take the Attack action again, however, they only get one weapon attack because Haste specifically limits the number of attacks to 1.
This is a specific restriction which overrides the number of attacks granted by Tenser's Transformation just as it supersedes the same exact ability as granted by Extra Attack.
Thus, a hasted, tenser-transformed wizard gets three weapon attacks.