ETHUSD is approaching the top line (400 USD) of an earlier large ascending triangle. After the breakout of an ascending triangle, it is not uncommon to see the price retrace to this top line to retest the support and validate the breakout, after which the asset normally rallies. Furthermore, on the linear scale, there is also a bullish trendline support in this region. Also, we have reached the area of the 78.6% fib retracement from the elliot impulse wave shown. Finally, the RSI is very oversold.
I must admit the elliot wave count is always a bit arbitrary, and an alternative version which isn't shown here has a 78.6% retracement at the dotted line (320 USD).
One entry strategy here is to wait for either a flash crash into support, which will surely exhaust sellers (at least for a while); but a safer entry would be to wait for a confirmed reversal and enter there. If ETHUSD is indeed simply retesting the ascending triangle formation, ETHUSD could go way higher in the future.